Power Equation Research Articles

Electric Field Intensity Assessment on Curved Wires for Domestic Installations

The increasing complexity of domestic electrical installations necessitates a thorough understanding of electric field intensity, particularly when dealing with curved wires. This paper presents the results on the assessment of the electric field intensity in curved wire configurations, which are commonly encountered in residential settings due to architectural constraints. This study employs both theoretical and simulation approaches with the help of the Finite Element Based Software (COMSOL Multiphysics). The theoretical and simulations were used for a case of straight wire to allow validation of the model through comparing simulation results with the theoretically computed electric field intensity using mathematical formula. Later on, the COMSOL Multiphysics were used to compute electric field intensity under various curvature radii. The results of maximum electric field intensity against curvature radii were then plotted as scatter in excel and then fitted by the equation from the trendline option. The results show that the curvature of wires significantly influences electric field distribution. The electric field intensity was observed to be much higher for a case of small curvature radius as compared to larger curvature radius. For example, for the type of the geometry presented in this paper to represent the PVC wire used in domestic buildings’ electrical installations, the maximum electric field intensity for curvature radius of 0.025 mm was observed to be about 7 times for a case when the curvature radius was 10 mm. In additional, the power equation was found to model well the relationship between the maximum electric field intensity and curvature radius of the geometry presented in this paper

Effect of the dissipative states of non-ideal second-type superconductors on their current-carrying capacity

The influence of the dissipative states of non-ideal second-type superconductors on their current-carrying capacity is investigated. The study performed is based on the numerical solution of non-stationary Maxwell and Fourier equations with different features of the non-linear rise of their I-V characteristics. First, the power equation of the I-V characteristic with various n-values was used to examine the states of superconductors that occur when the I-V characteristic continuously increases. Second, the obtained results are compared with the results of computer experiments simulating the thermo-electrodynamic states of superconductors when the electric field is not present in their I-V characteristics in the subcritical current range. A piecewise linear I-V equation describes such idealized modes. The results of the simulations indicate that a superconductor's ability to carry the transport current drops as the n-value decreases. Accordingly, the maximum transport current (quench current) flowing stably through a superconductor with an idealized I-V characteristic are always higher than the corresponding value calculated for superconductor with the same critical current but with a continuously increasing I-V characteristic. Moreover, a deterioration in cooling conditions or an increase in the current charging rate will also lead to a reduction in the current-carrying capacity of non-ideal second-type superconductors. The non-trivial temperature change of superconductors during formation of stable modes should necessarily be taken into account in experiments to investigate the voltage-current characteristics of superconductors, their current-carrying capacity, and loss theory.

A novel approach for analyzing linear amplitude sweep (LAS) test data of asphalt binders

Fatigue cracking is one of the crucial distresses considered for the design of flexible pavements. The initiation of fatigue cracking occurs in the binder phase of an asphalt mixture. The linear amplitude sweep (LAS) test was developed to analyze the fatigue damage in the asphalt binder. AASHTO T391 provides a method to analyze the LAS test data by fitting a power equation between the fatigue parameter (G*sinδ) and damage intensity. This method has some inherent weaknesses of overfitting or underfitting of the data at different damage levels. This study proposes a new method where a total curve is divided into two parts that fit the data in two different equations and then sum them up. The first part comprises of the data up to cumulative damage corresponding to the maximum effective stress, and the second part consists of accumulated damage in the material till it reaches the maximum strain (30 %). This method is called the bifurcation method in this paper. LAS test data of 27 long-term aged bitumen samples having different physical properties is used to determine the number of fatigue life cycles (Nf) by these two methods, and results are compared in terms of mean absolute percentage error (MAPE), root mean square error (RMSE), and residual sum of squares (RSS). It is shown that there is a significant reduction in the errors when the data fitting was done using the proposed bifurcation method. Further, the ranking was allotted to the samples based on the number of fatigue life cycles (Nf) at three different strain levels (2.5 %, 5 %, and 10 %) at intermediate-temperature conditions estimated using two methods. The shift indicator parameter was used to analyze the variability in the ranking of the samples due to changes in the strain levels. The study concludes that the proposed bifurcation method fits the predicted values more accurately than the prescribed power law.

Neonatal reference values and nomograms of systemic vascular resistances estimated with electrical cardiometry.

Scanty data are available about neonatal systemic vascular resistances (SVR). We aim to provide reference values and nomograms for neonatal SVR. Multicenter, cross-sectional,descriptive study performed in France and Italy. Neonates with complete hemodynamic stability were enrolled. Non-invasive measurements of SVR by electrical cardiometry performed once, after the first 72 h and before the 7th day of postnatal age. We studied 1094 neonates: SVR was correlated with gestational age (ρ = -0.55, adj-r = -0.46, p < 0.001) and birth weight (ρ = -0.59, adj-r = -0.45, p < 0.001) irrespective of newborn sex. The relationships between SVR, gestational age and birth weight were represented by power equations and SVR was decreasing with increasing age and weight. Age- and weight-based SVR nomograms had optimal goodness-of-fit (non-linear R2 ≥0.74). Similar results were obtained for body surface indexed-SVR. In hemodynamically stable neonates, SVR decrease with increasing gestational age and birth weight. Specific gestational age and birth weight-based nomograms are provided for the clinical interpretation.

Data transformation and model selection in bivariate allometry.

Students of biological allometry have used the logarithmic transformation for over a century to linearize bivariate distributions that are curvilinear on the arithmetic scale. When the distribution is linear, the equation for a straight line fitted to the distribution can be back-transformed to form a two-parameter power function for describing the original observations. However, many of the data in contemporary studies of allometry fail to meet the requirement for log-linearity, thereby precluding the use of the aforementioned protocol. Even when data are linear in logarithmic form, the two-parameter power equation estimated by back-transformation may yield a misleading or erroneous perception of pattern in the original distribution. A better approach to bivariate allometry would be to forego transformation altogether and to fit multiple models to untransformed observations by nonlinear regression, thereby creating a pool of candidate models with different functional form and different assumptions regarding random error. The best model in the pool of candidate models could then be identified by a selection procedure based on maximum likelihood. Two examples are presented to illustrate the power and versatility of newer methods for studying allometric variation. It always is better to examine the original data when it is possible to do so.

Analytical method of incorporating failure probability to predict the fatigue life of ultra-high-performance concrete (UHPC)

This study predicted the fatigue life (N) of UHPC incorporated with different volume fractions (Vf = 0.0%, 0.5%, 1.0%, 1.5% and 2.0%) of steel fiber under flexural cyclic loading at various stress levels (S). The Weibull distribution, a two-parameter model, was utilized to estimate the distribution of fatigue life in UHPC. Subsequently, three methods were employed to calculate the parameters: the graphical method, the method of moments, and the method of maximum likelihood. The averaged values of these parameters were then obtained to enhance the accuracy of the estimation. The results are presented in the form of S-N diagrams, which depict the quantitative relationship between stress (S) and fatigue life (N). This relationship was determined using the Wohler equation, the modified Wohler equation, and the power equation. By employing these equations, the flexural fatigue strength of UHPC can be accurately predicted. Subsequently, the fatigue failure probability (Pf) was incorporated to enhance the reliability of the S-N quantitative relation. The fatigue testing results were presented in the form of S-N-Pf curves, which comprehensively reflect the relationship between stress, fatigue life, and failure probability. Furthermore, the mathematical relation of the S-N-Pf curves was derived to predict the fatigue life of UHPC with a given failure probability, providing a more comprehensive and accurate assessment of its fatigue behavior.

Finite deformation peridynamics shell theory: Application to mechanical metasurfaces

A finite deformation Simo-Reissner peridynamics (PD) shell theory is developed to investigate wave propagation and crack growth in shell structures. Simo-Reissner deformation approximation is utilized to derive the governing equations of the proposed theory from the three-dimensional PD equation. Deformation states for the PD shell theory are identified from the reduced stress power equation. Classical shell constitutive equations are seamlessly incorporated in PD framework by constitutive correspondence approach where a particular form of the classical reduced stress power expression suitable for constitutive correspondence is used. Rotation tensor is updated using an exponential map. A new bond breaking criterion is proposed for PD shell based on critical stretch and critical relative rotation. The solutions of the PD shell governing equations for quasi-static and dynamic cases are obtained through the Newton-Raphson method and the Newmark-beta method, respectively. Numerical simulations include finite deformation of cylindrical shell under both quasi-static and dynamic loading conditions. The PD shell model is validated against finite element solutions obtained using ANSYS®. Crack propagation through the cylindrical shell is simulated under quasi-static and dynamic loading. Wave propagation through cylindrical shell embedded with periodically arranged holes and cracks is investigated. Significant wave attenuation and large bandgap demonstrates the efficacy of the present proposal.

Mechanical Power in Decelerating Flow versus Square Flow Ventilation in Pediatric Acute Respiratory Distress Syndrome.

Mechanical power is a summary variable quantifying the risk of ventilator-induced lung injury. The original mechanical power equation was developed using square flow ventilation. However, most children are ventilated using decelerating flow. It is unclear whether mechanical power differs according to mode of flow delivery. This study compared mechanical power in children with acute respiratory distress syndrome who received both square and decelerating flow ventilation. This was a secondary analysis of a prospectively enrolled cohort of pediatric acute respiratory distress syndrome. Patients were ventilated on decelerating flow and then placed in square flow and allowed to stabilize. Ventilator metrics from both modes were collected within 24 h of acute respiratory distress syndrome onset. Paired t tests were used to compare differences in mechanical power between the modes. This study enrolled 185 subjects with a median oxygenation index of 9.5 (interquartile range, 7 to 13) and median age of 8.3 yr (interquartile range, 1.8 to 14). Mechanical power was lower in square flow mode (mean, 0.46 J · min-1 · kg-1; SD, 0.25; 95% CI, 0.42 to 0.50) than in decelerating flow mode (mean, 0.49 J · min-1 · kg-1; SD, 0.28; 95% CI, 0.45 to 0.53) with a mean difference of 0.03 J · min-1 · kg-1 (SD, 0.08; 95% CI, 0.014 to 0.038; P < 0.001). This result remained statistically significant when stratified by age of less than 2 yr in square flow compared to decelerating flow and also when stratified by age of 2 yr or greater in square flow compared to decelerating flow. The elastic contribution in square flow was 70%, and the resistive contribution was 30%. Mechanical power was marginally lower in square flow than in decelerating flow, although the clinical significance of this is unclear. Upward of 30% of mechanical power may go toward overcoming resistance, regardless of age. This is nearly three-fold greater resistance compared to what has been reported in adults.

Lessons from business education's online transition: A Saudi Arabian case study

We survey business school faculty and students from a major Saudi Arabian university that transitioned to online learning because of the COVID-19 lockdown. This study leverages the Unified Theory of Acceptance and Use of Technology (UTAUT) framework to explore the factors influencing faculty and student willingness and acceptance of online learning as we move to a post-COVID-19 new normal. We use partial least square structural equation modeling to examine the factors that impact faculty and student satisfaction and their behavioral intention to the continued use of online learning in the future. The results of the study indicate that when faculty perceive that e-learning improves their teaching performance and effectiveness (performance expectancy) and find that online teaching tools are relatively easy to use (effort expectancy) then they are more open to consider online teaching and using digital tools even after the pandemic. Further analysis, however, indicates that as faculty perceive a greater loss of control in the classroom, they are less likely to consider teaching/learning online courses and using digital tools in the future. Like faculty, students value online learning when they perceive it helps improve their learning and performance (performance expectancy) and find that e-learning tools are easy to use (effort expectancy) but in contrast to faculty, image, and peer pressure (Social influence) also plays an important role in their acceptance of online learning. Additionally, the changing classroom dynamics, specifically the professor-student power equation under online teaching, is less of a concern for students as compared to faculty.

Evolving scientific discovery by unifying data and background knowledge with AI Hilbert

The discovery of scientific formulae that parsimoniously explain natural phenomena and align with existing background theory is a key goal in science. Historically, scientists have derived natural laws by manipulating equations based on existing knowledge, forming new equations, and verifying them experimentally. However, this does not include experimental data within the discovery process, which may be inefficient. We propose a solution to this problem when all axioms and scientific laws are expressible as polynomials and argue our approach is widely applicable. We model notions of minimal complexity using binary variables and logical constraints, solve polynomial optimization problems via mixed-integer linear or semidefinite optimization, and prove the validity of our scientific discoveries in a principled manner using Positivstellensatz certificates. We demonstrate that some famous scientific laws, including Kepler’s Law of Planetary Motion and the Radiated Gravitational Wave Power equation, can be derived in a principled manner from axioms and experimental data.

An Adaptive Virtual-Impedance-Based Current-Limiting Method with the Functionality of Transient Stability Enhancement for Grid-Forming Converter

Grid-forming (GFM) converters are regarded as the most promising solution for grid-connected converters of renewable energy due to their robustness against weak grids. However, attributable to their voltage source characteristics, GFM converters may experience overcurrent issues during large disturbances. The virtual impedance (VI) method is an effective method to solve this problem. Nevertheless, there exists a contradiction between the demands for VI posed by current limitations and transient stability. Firstly, the analytical equations of virtual impedance for limiting the fault steady-state current of a GFM converter with different depths of grid voltage sag are solved. On that basis, an adaptive method based on virtual impedance is proposed to limit the fault current. Moreover, the analytical equation of the output active power of the converter when using adaptive virtual impedance to limit the fault current is solved. On this basis, the effect of the virtual impedance ratio on the transient stability is investigated. Finally, an adaptive virtual-impedance-based current-limiting method with the functionality of transient stability enhancement for a grid-forming converter is innovatively proposed. The enhancement effect of the method is verified by the equal area criterion method and phase portrait method. Finally, the efficacy of the proposed method in limiting fault currents and enhancing transient stability is validated through hardware-in-the-loop (HIL) experiments.

Graphene thermionic energy converter integrated with two-stage thermoelectric generator for energy cascade utilization

For the purpose of energy cascade utilization, a new coupling system consisting of a graphene-based thermionic energy converter and a two-stage thermoelectric generator is proposed, in which the waste heat of graphene-based thermionic energy converter is recovered by the two-stage thermoelectric generator for generating extra power. Based on thermionic emission, semiconductor physics, and non-equilibrium thermodynamics, mathematical equations for power, efficiency, and exergy efficiency of the coupling system are presented, and the general performance features of the hybrid system are revealed. Numerical analysis shows that the maximum efficiency, maximum power density, and maximum exergy efficiency of the coupling system are 54.99%, 7.93Wcm−2, and 68.75%, respectively. Moreover, the maximum efficiency and maximum power density of the coupling system are enhanced by 28.39% and 28.52%, respectively, and the maximum exergy efficiency is improved by 28.39% compared to the stand-alone graphene-based thermionic energy converter. Subsequently, comprehensive parametric analyses are carried out to derive the effects of the heat source temperature, Fermi level of graphene, cathode work function, semiconductor element area-length ratio, and the Thomson effect on the performance of the coupled system. The obtained results may be useful for the design and running of this kind of energy cascade utilization system.

Gendered subalternity in Khwabnama

ABSTRACT As an insightful literary text exploring segments of labyrinthine South Asian peoples’ history, Akhtaruzzaman Elias’ Khwabnama (1996, the title translates as “The Narrative of Dreams”) is a fictional account of peasantry around the beel (marshlands) regions of present-day northern Bangladesh. The novel is set against the Tebhaga movement of the 1940s that demanded two-thirds share of the crops for landless sharecroppers. This is to be read in the light of the emergent (East) Pakistan movement that peddled dreams of Muslim subaltern ascendancy, once Partition had displaced predominant Hindu landlords. The bulk of Elias’ characters are, however, “the colonised subaltern subject(s),” who undergo only a de-facto transference of thralldom under nouveau riche Muslim landowners. Contrary to vaunted dreams (khwab) therefore, the poor peasants were never to emerge into any centrality of power equations. From the perspective of gendered subaltern representation, Khwabnama explores Elias’ partial dismantling of the sexual division of labour that Gayatri Spivak disavows as a colonial and phallocentric construct. Notwithstanding that the majority of women characters are hemmed in by mundaneness and carnality, and lack agency to approximate the cultural or political aspirations of their male counterparts; there are still a few who are physically strong and equal sharers with men in agrarian productivity. In the light of these observations, this paper reads Khwabnama as a text of masculinity that attempts a recreation of subaltern history, while effacing the “itinerary of the subaltern” female, at a critical juncture of Bangladeshi historiography.

Analysis and design of a GHz bandwidth adaptive bias circuit for an mmW Doherty amplifier

This paper derives theoretical results for adaptive bias in Doherty amplifiers and presents the design and measurements of an integrated adaptive bias circuit tailored for high peak-to-average high bandwidth signals. Fundamental equations for output power, impedance, and efficiency of the complete Doherty amplifier are derived. Even with ideal transistor models, the Doherty amplifier is fundamentally nonlinear due to saturation of the main amplifier and class-C nonlinearity of the auxiliary. Increasing the transconductance of the auxiliary amplifier mitigates the distortion. Adaptive bias offers the possibility to control the output current characteristic of the auxiliary amplifier. This means that adaptive bias linearises and mitigates the need for an oversized auxiliary amplifier. Both methods, transconductance scaling and adaptive bias, are analysed and compared as well as having a band limited adaptive bias signal. The design of a multiple GHz bandwidth adaptive bias circuit is presented. To verify the circuit design and the theoretical predictions, an mmW Doherty amplifier in 22 nm CMOS-FD-SOI, utilizing the presented adaptive bias circuit, is measured and compared with and without adaptive bias. Comparison is conducted both using continuous-wave and modulated high bandwidth signals. Measured results confirm the predicted improvements by the adaptive bias as derived by the theoretical analysis.

Fluctuating pressure gradients and corrugated surfaces effects on wind turbines power output

This paper investigates the effect of corrugated surfaces on the wind turbines power output for both laminar and turbulent flows. Conservation principles including continuity and momentum equations, wind turbine power equations, and the corrugated surface equation have been implemented to build up a theoretical model then which has been solved using MATLAB. This model simulates wind turbines power output and analyzes several case studies implementing different parameters such as air pressure wave amplitude (Po), air wave fluctuation frequency (n), and wind layer turbulence (b). Also, different complex terrains in two main scenarios representing two different positions (X) of the wind turbine are analyzed. This analysis indicates the importance of wind turbines micro siting. In addition, it is found that increasing the pressure ratio increased wind turbine power output, while increasing the frequency decreased the power ratio of the wind turbines for both laminar and turbulent flow conditions. Increasing turbulence for the turbulent model increased the power ratio.

AN ENGINEERING APPROACH TO THE STUDY OF THE PROCESSES OF DOUGH FLOW IN THE PRODUCTION OF PASTA AT AGRO-INDUSTRIAL ENTERPRISES

Background. In modern conditions, the provision of domestic pasta produced from durum wheat varieties on modern technological equipment is becoming important. At the same time, the quality of the finished pasta is also determined by the rheological properties of the pasta dough when passing through the pasta press matrix, which determined the purpose of the study to develop a method of computational evaluation for calculating the relationship between the speed parameters of the flow of pasta dough in the cylindrical sections of the channels of the molding matrix with pressure drops to overcome viscous resistance, the dimensions of the structural elements of the channel, as well as with indicators of the rheological properties of pasta dough. Materials and methods. To study the flow of pasta dough, baking flour of the highest grade M-54 28 was chosen as a raw material in stepped cylindrical channels. The applied rheological model is described and a technique for mathematical modeling of the flow parameters of pasta dough in cylindrical channels is given. Due to the small contribution of the pasta dough shear strength to the total pressure loss, a rheological model of a nonlinear-viscous medium is used, which is described by a power equation containing physically determined constants. Neglecting the elastic deformations of the dough due to their smallness, we assumed the condition of constancy of the volumetric productivity for each cross section of the channel. Results. Analytical dependencies are presented that relate the change in velocity over the channel cross section to the pressure developed necessary to overcome the viscous resistance, as well as to the radii and length of the channel, and to the rheological properties of the pasta dough. These dependences formed the theoretical basis of the method for calculating the parameters of pasta dough flow in cylindrical channels. Conclusion. On the example of an industrial matrix of a pasta press, made in the form of a system of cylindrical channels of a stepped-variable diameter in the preforming zone, calculations were made to determine the average and maximum flow rates of pasta dough in each section of the channel and the developed pressure. The results of the research can be used in engineering practice when designing new matrices for forming pasta dough and in the production processes of enterprises to calculate their production capacities.

A Method for Specifying Complete Signature Randomization and an Algebraic Algorithm Based on It

To eliminate the limitations of signature randomization in known algebraic algorithms with a hidden group, the security of which is based on the computational complexity of solving large systems of power equations, a method for ensuring complete randomization is proposed. Based on this method, a new algorithm of the indicated type was developed, using a four-dimensional finite non-commutative associative algebra as an algebraic basis. We obtained estimates of the security of algorithms to direct attacks as well as from attacks based on known signatures, which confirm the effectiveness of the proposed signature randomization method. Due to the relatively small size and signature of the public and private keys, the developed algorithm is of interest as a potential practical post-quantum digital signature scheme.

A 1750nm thulium-doped optical fiber laser design: Theoretical model and code simulation

This article mainly studies the physical model design and code simulation of a thulium-doped fiber laser that outputs 1750nm laser. The optical fiber laser has been widely used due to its excellent performance compared with other solid-state laser devices. Among all types of fiber lasers, ytterbium-doped fiber lasers possess the highest output power, whereas they seem to be impractical when an output laser with a longer wavelength is required. However, Thulium-doped lasers have huge room for development to solve the problem, whose unique center wavelength characteristics provide them with huge utilization value. This article shows the electronic transition process a of thulium-doped laser and the power transmission diagram in the fiber. Its rate equation and power equation are also listed below. Through paper retrieval and data extraction, the values of laser parameters can be accurately confirmed, and its power curve can also be obtained through simulation. After analyzing the data obtained from the simulation, the working principle of the fiber laser was intuitively displayed, and the performance of the system was further evaluated. Last but not least, several limitations of this experiment will also be discussed, in order to explore the system more thoroughly.

Research on the minimum network loss optimization control strategy of the active distribution network based on the distributed power flow controller

With large-scale access to distributed new energy, the power flow form of the distribution network tends to be complex. The distribution loop network rate increases, resulting in serious circulation of the distribution network, which places significant pressure on the loss of the distribution network. The problem of network loss change caused by distributed new energy grid connection, coupled with the inconsistency between load fluctuation and output power change of distributed new energy, will have a significant impact on the safety, reliability, and economic operation of the distribution network. Therefore, it is urgent to have good economic and technical means of power flow control. This paper proposes a minimum network loss optimization control strategy for active distribution networks based on a distributed power flow controller. First, according to the characteristics of the distribution network load and the new energy power supply along the distribution line, the multiple sub-modules of the distributed power flow controller are arranged in sections in the distribution loop network line. The regulation effect of the distributed power flow controller on the voltage and power flow of the distribution loop network is analyzed. The loop network current equation and power loss equation after the distributed power flow controller are constructed, and the power equation with the minimum active loss of the active distribution loop network is derived. Second, the control strategy for minimum network loss of the active distribution network based on the distributed power flow controller is proposed. Finally, the simulation model of the active distribution loop network is constructed by PSCAD/EMTDC. The loss of the loop network before and after the distributed power flow controller is simulated and analyzed, and the effectiveness of the proposed strategy is verified.

Radiation induced non-linear oscillations in ITER baseline scenario plasmas in DIII-D

This work shows how the radiation brought about by metals or metal-equivalent radiators such as Kr and Xe produces non-linear dynamics on otherwise stationary β N flattops of DIII-D ITER Baseline Scenario demonstration discharges. The Kr and Xe gases are used to reproduce the radiative loss rates of W in present machines that operate at core temperatures much lower than the expected ITER temperature. Experiments on DIII-D with injection of Kr and Xe, as well as with sources of intrinsic metals reach the range of radiated fraction values expected in the ITER core and experience slow oscillations in temperature and radiated power. In many cases of high radiated fraction, the core temperature decreases enough for the safety factor profile to rise above the 1/1 rational surface, naturally eliminating sawteeth and occasionally producing a persistent helical core. The oscillations can be reproduced by a modified Lotka–Volterra system for temperature and radiated fraction if diffusion and noise are included, which indicates that the interplay between temperature and radiation can be the main cause of the cyclic nature of the system. A new physics based model which includes equations for temperature, density and input power can also reproduce the oscillations observed in the experiments. The present results suggest that the non-linearity of the system can be increased by the inclusion of the inherently non-linear alpha heating term, which is proportional to ∼n e 2 T i 2, and obtains oscillations in the model when added to an otherwise more stationary system.