Power Equation Research Articles

Low Order Harmonics Elimination in Multilevel Inverters Using Gradient Descent Algorithm

In recent years, the topic of harmonics in general and the elimination of low order harmonics in power system in particular attracts the attention of many researchers in the field of power electronics. Estimation of the values of switching angles in multilevel inverters has been of interest in reduction or elimination of low order harmonics. In this paper, the technique that is based on the gradient or steepest descent algorithm is described. This algorithm searches for the minimum value of the power harmonic distortion of the low order harmonics in the output waveform, according to the value of the modulation index set at the beginning of the optimization process. The power equations of harmonics are used for this purpose and therefore a high convergence rate is obtained with this method. The results have been verified by MATLAB software.

Computational and numerical analysis of AC optimal power flow formulations on large-scale power grids

Alternating current optimal power flow (AC-OPF) is a fundamental tool in electric utilities to determine optimal operation of the various resources. Typically, the AC-OPF problem uses power balance formulation containing voltages and power equations. Yet, there is no comprehensive comparison of the different AC-OPF formulations, especially for large-scale networks. This paper presents a detailed comparative evaluation of different formulations of the AC-OPF problem on networks ranging from 9-bus to 25,000 buses. Three different formulations: 1) power balance with polar voltages, 2) power balance with Cartesian voltages, and 3) current balance with Cartesian voltages are discussed in detail by comparing their characteristics, and numerical and computational performance. We compare the performance of the three methods in terms of computational speed, number of iterations, and number of non-zeros in Jacobian and Hessian matrix. The numerical results show that power balance polar formulation had the best performance on small number of bus system but on a large-scale test grid current balance cartesian outperformed the other two formulations.

К ИЗУЧЕНИЮ БИОЭКОЛОГИИ КРЕВЕТОК КАСПИЯ

Only two species of shrimps live in the Caspian Sea: Palaemon elegans and P. adspersus (Crustacea, Decapoda: Palaemonidae), which were introduced to the Caspian Sea in 1931-1934 during the introduction of mullets. Data on the biology of these species of shrimps are reflected only in the works by E.N. Kudelina (1950) and M.P. Marochkina (1980). This determines the relevance of research on the current state of the Caspian shrimp population. The material was collected in various areas of the Middle Caspian Sea in the summer-autumn period. Both species live up to five meters deep. P. elegans prefer coastal underwater objects with dense thickets, P. adspersus - open shallow waters with sandy-muddy soil. To the north of Makhachkala, P. elegans predominates, to the south, the number of both species is the same, and to the east, P. adspersus dominates. The characteristics of breeding females are presented, and the dependence of fecundity on the length of egg-bearing females is revealed. The absolute fecundity increased with the increase in the size of the females. Regression equations reflecting the relationship between fecundity and length of egg-bearing females of P. elegans and P. adspersus are calculated, expressed by power equations, respectively: E = 0.044947 · L265356 and E = 2.323 · L17.4, where: E - fecundity, L-length. In October 2017, in May and October 2018, several specimens of the subtropical freshwater shrimp Macrobrachium nipponense were found downstream of the Terek River. Probably, in the near future, the species composition of the Caspian shrimp will be replenished with another species.

Developing the Estimating Equations for Muscle Power by Analysis of Reliability and Validity on Different Versions of Wingate Anaerobic Test Setting

PURPOSE The purpose of this study was to develop the estimating equations for 4 types of Wingate Anaerobic test setting.METHODS 80 male elite athletes performed 4 trials of the Wingate Anaerobic test by each type. Subjects were conducted the retest one week later. Data collected from the Wingate Anaerobic test included mean power, peak power, and power drop for 30s were measured. Coefficient of correlation was used for validity of type 1(DOS version) and the other types(ver. 2.24, 3.3.0, and 3.2.1). Pearson’s correlation coefficient was used to examine the reliability of test and retest. Simple regression analysis was used for calculating the estimating equation.RESULTS There was significant correlation for absolute value(Watt, p<.01) and relative value(Watt/kg, p<.01) of mean power, absolute value(W, p<.01), relative value(Watt/ kg, p<.05), and power drop rate(%, p<.01). Test and retest reliability was excellent for all test variables(p<.01).CONCLUSIONS From the all results, the estimating equation was calculated to convert all outputs from each type to the other types of the Wingate Anaerobic test setting. These findings suggest that the estimating equations are compatiable to 4 types of Wingate Anaerobic test setting.

Why do large rivers tend to form multichannel? A field study in the Upper Paraná River

Anastomosed rivers include a diverse group of fluvial forms with multiple and interconnected alluvial channels. They occur in a wide range of climates and reliefs and constitute the typical pattern of the mega rivers (Qm> 17,000 m3s-1). Several authors have assumed that the development of an anabranching formation is the mechanism by which a channel maintains its maximum efficiency. However, this has only been tested by mathematical studies. In this study, we confirm this theory in a 58-km anabranching reach of the Upper Paraná River, through a hydraulic and bathymetric survey of 14 cross-sections. We conclude that where the slope can'tincrease, the channel reduces its w:d ratio, thereby maintaining its efficiency in the wider sections, according to the specific stream power equation (ω=ρgQs/w). The channel width and alluvial plain width are controlled by allochthonous factors (tectonic lineaments and bank composition). Although the nodal sections have the greatestefficiency, we confirmed that flow efficiency is maintained at a constant level of bedload transport and specific stream power along the anabranching reach.

Intra-operative ventilator mechanical power as a predictor of postoperative pulmonary complications in surgical patients: A secondary analysis of a randomised clinical trial.

BACKGROUNDStudies in critically ill patients suggest a relationship between mechanical power (an index of the energy delivered by the ventilator, which includes driving pressure, respiratory rate, tidal volume and inspiratory pressure) and complications.OBJECTIVEWe aimed to assess the association between intra-operative mechanical power and postoperative pulmonary complications (PPCs).DESIGNPost hoc analysis of a large randomised clinical trial.SETTINGUniversity-affiliated academic tertiary hospital in Melbourne, Australia, from February 2015 to February 2019.PATIENTSAdult patients undergoing major noncardiothoracic, nonintracranial surgery.INTERVENTIONDynamic mechanical power was calculated using the power equation adjusted by the respiratory system compliance (C RS). Multivariable models were used to assess the independent association between mechanical power and outcomes.MAIN OUTCOME MEASURESThe primary outcome was the incidence of PPCs within the first seven postoperative days. The secondary outcome was the incidence of acute respiratory failure.RESULTSWe studied 1156 patients (median age [IQR]: 64 [55 to 72] years, 59.5% men). Median mechanical power adjusted by C RS was 0.32 [0.22 to 0.51] (J min−1)/(ml cmH2O−1). A higher mechanical power was also independently associated with increased risk of PPCs [odds ratio (OR 1.34, 95% CI, 1.17 to 1.52); P < 0.001) and acute respiratory failure (OR 1.40, 95% CI, 1.21 to 1.61; P < 0.001).CONCLUSIONIn patients receiving ventilation during major noncardiothoracic, nonintracranial surgery, exposure to a higher mechanical power was independently associated with an increased risk of PPCs and acute respiratory failure.TRIAL REGISTRATIONAustralia and New Zealand Clinical Trials Registry no: 12614000790640.

Short communication: Analytical models for 2D landscape evolution

Abstract. Numerical modelling offers a unique approach to understand how tectonics, climate and surface processes govern landscape dynamics. However, the efficiency and accuracy of current landscape evolution models remain a certain limitation. Here, I develop a new modelling strategy that relies on the use of 1D analytical solutions to the linear stream power equation to compute the dynamics of landscapes in 2D. This strategy uses the 1D ordering, by a directed acyclic graph, of model nodes based on their location along the water flow path to propagate topographic changes in 2D. This analytical model can be used to compute in a single time step, with an iterative procedure, the steady-state topography of landscapes subjected to river, colluvial and hillslope erosion. This model can also be adapted to compute the dynamic evolution of landscapes under either heterogeneous or time-variable uplift rate. This new model leads to slope–area relationships exactly consistent with predictions and to the exact preservation of knickpoint shape throughout their migration. Moreover, the absence of numerical diffusion or of an upper bound for the time step offers significant advantages compared to numerical models. The main drawback of this novel approach is that it does not guarantee the time continuity of the topography through successive time steps, despite practically having little impact on model behaviour.

Overland flow resistance and its components for slope surfaces covered with gravel and grass

Overland flow resistance plays an important role in predicting hillslope hydrological and erosion processes on hillslopes. Soil surfaces covered with grass and/or gravel may increase hydraulic resistance to overland flow, but there is little information on the determination on these resistance components in a composite slopeland. In this study, the smooth and sand-bed surfaces covered with different gravel or/and grass (cover degree = 2.5%, 5%, 10%, 15%, 20%) under five slope gradients (3°, 6°, 9°, 12°, 15°) were subjected to inflows to investigate the hydraulic resistance and validate the sum law of resistance components. The results showed that, the overland flow mainly belonged to transition or turbulent and supercritical flow regime with 150 < Re < 2050 and 0.4 < Fr < 6.9. As the gravel or grass cover increased, Darcy-Weisbach resistance coefficient (f) significantly increased. The resistance can be well predicted by flow discharge, gravel or grass cover using a power equation. The flow discharge had a greater influence on flow resistance than gravel or grass cover, and the impact of flow discharge weakened with the increasing bed slopes. The total resistance was generally greater than the sum of resistance components, and there existed a positive additional resistance for the composite surfaces. The additional resistance accounted for 37.4%, 4.2% and 16.6% to the total resistance for the sand surfaces covered with gravel, grass and both of them, respectively. These results can help to understand the rainfall-runoff processes and improve the design of soil and water conservation measures in the rocky and mountainous areas.

Prioritizing Energy-Intensive Machining Operations and Gauging the Influence of Electric Parameters: An Industrial Case Study

Increasing the energy efficiency of machining operations can contribute to more sustainable manufacturing. Therefore, there is a necessity to investigate, evaluate, and optimize the energy consumed during machining operations. The research highlights a method employed to prioritize the most energy-intensive machining operation and highlights the significance of electric parameters as predictors in power estimation of machining operations. Multi regression modeling with standardized regression weights was used to identify significant power quality predictors for active power evaluation for machining operations. The absolute error and the relative error both decreased when the active power was measured by the power analyzer for each of the identified machining operations, compared to the standard power equation and that obtained from the modeled regression equations. Furthermore, to determine energy-intensive machining operation, a hybrid decision-making technique based on TOPSIS (a technique for order preference by similarity to ideal solution) and DoM (degree of membership) was utilized. Allocation of weights to energy responses was carried out using three methods, i.e., equal importance, entropy weights, and the AHP (analytical hierarchy process). Results revealed that a drilling process carried out on material ST 52.3 is energy-intensive. This accentuates the significance of electric parameters in the assessment of active power during machining operations.

TREND MODELS OF FOREST INDUSTRY INDICATORS

The article analyzes the main indicators of the forest industry of Ukraine and Khmelnytsky region. The state of timber harvesting by types of products is shown, it is noted that since 2017 there is no financing of the forest industry by the state, so forestries have to manage independently from their own sources. The paper considers the problem of modeling the indicators of the forest industry of the regions with the help of economic and mathematical methods and models. Trend models have been chosen as a research tool, with the help of which the equations of power, logistic, exponential dependences and polynomials of the second and third degrees are obtained. The constructed models are evaluated according to the criteria of determination and the forecast values for the following periods are determined. The results of calculations can be used in management decision-making systems as a source of data for further calculations. The obtained forecasts of forest industry indicators showed the importance of investing in the forest industry. Preservation, rational use and increase of resources of the forest treasury - so it is possible to define the main tasks facing the forestry of Ukraine. The issue of reforestation, creation of forest plantations in the volumes exceeding fellings, improvement of their qualitative structure and productivity remains paramount in the importance and urgency. Given the current situation in the country's forestry and in order to solve the problem of ecologically balanced forest management as a factor of sustainable socio-economic development, it is necessary to apply a comprehensive approach based on the use of economic and mathematical methods and models. This allows you to take into account technical, economic, environmental, organizational, social and other aspects of management, as well as see their relationship. One of the means of balanced management is modeling and forecasting trends in the main indicators of the forest industry both at the regional level and in the country as a whole.

Study of the properties of materials under complicated conditions of low cycle deformation

Operational integrity of structures under complex combined modes of a loading depends on a significant number of combinations of operational parameters of thermomechanical impacts in part of loads, temperatures, duration, number of cycles, and deformation rates. The main laws governing the deformation of structural materials under complex loading are determined in conditions of combined standard, unified and special tests in laboratories. Using representative substantiations of physical and mechanical models for deformation diagrams in a wide range of loading conditions, taking into account the different scales of models, the structure of materials and the responsibility of structures, a stepwise consideration of the corresponding types of deformation is proposed: elastic, sign-variable flow, progressing accumulation of strains and their combination. At the same time, calculations of the structures can be carried out in the form of a hierarchical system in which each next level specifies the boundaries of permissible impacts towards expansion of the range of acting loadings, temperatures, rates and modes of deformation, which entails an increase in the bulk of the required initial data and complicates the calculations. The proposed methods of schematization of the physicomechanical properties and types of the equations of state for description of the deformation curves take into account the requirements of compactness of the initial data and the need of using both standard and unified methods for determining the characteristics of cyclic inelastic deformation and special methods as well. To describe the kinetics of deformation diagrams under aforementioned conditions both from the theoretical point of view and from the point of view of practical applications, power equations appeared most suitable; to reflect the role of the temperature factor exponential dependences should be used; whereas power dependences are useful to take into account time factors, strain rate, and conditions of two-frequency loading. The refined calculations at the higher and more complicated steps of the considered hierarchy providing the maximum possible use of the deformation and strength reserves of the materials and structures are to be based on the kinetic laws describing processes of low cycle deformation under complex modes of loading.

Using different methods for calculating frontal alpha asymmetry to study its development from infancy to 3 years of age in a large longitudinal sample.

Frontal electroencephalography (EEG) alpha asymmetry (FAA), defined as the difference in frontal alpha power observed over the right and left frontal scalp regions, has been widely used in developmental research as a measure of multiple aspects of child behavior, such as temperament. Studies have used different equations to calculate FAA, which renders comparison of results across studies challenging. Furthermore, few studies have examined FAA's longitudinal stability across infancy and early childhood, which is a desirable feature of a temperament measure. We investigated the cross-sectional and the longitudinal correlations of FAA values from four different equations to calculate FAA used in the literature. We used baseline EEG data from a longitudinal sample of 321 infants and 168 3-year-old children (149 of whom had data at both timepoints). Consistent with previous work, FAA values calculated using two commonly used equations were highly correlated with each other cross-sectionally but not with values from a different equation that used log-transformed relative power. The log-transformed relative power FAA values were the only values that showed significant longitudinal stability. These findings suggest that researchers interested in FAA as a trait-like measure in children should consider using the relative power equation that renders stability across ages.

TSO-DSO Coordination Schemes to Facilitate Distributed Resources Integration

The incorporation of renewable energy into power systems poses serious challenges to the transmission and distribution power system operators (TSOs and DSOs). To fully leverage these resources there is a need for a new market design with improved coordination between TSOs and DSOs. In this paper we propose two coordination schemes between TSOs and DSOs: one centralised and another decentralised that facilitate the integration of distributed based generation; minimise operational cost; relieve congestion; and promote a sustainable system. In order to achieve this, we approximate the power equations with linearised equations so that the resulting optimal power flows (OPFs) in both the TSO and DSO become convex optimisation problems. In the resulting decentralised scheme, the TSO and DSO collaborate to optimally allocate all resources in the system. In particular, we propose an iterative bi-level optimisation technique where the upper level is the TSO that solves its own OPF and determines the locational marginal prices at substations. We demonstrate numerically that the algorithm converges to a near optimal solution. We study the interaction of TSOs and DSOs and the existence of any conflicting objectives with the centralised scheme. More specifically, we approximate the Pareto front of the multi-objective optimal power flow problem where the entire system, i.e., transmission and distribution systems, is modelled. The proposed ideas are illustrated through a five bus transmission system connected with distribution systems, represented by the IEEE 33 and 69 bus feeders.

Variability of rill detachment capacity with sediment size, water depth and soil slope in forest soils: A flume experiment

Rill detachment is the most important erosive process in steep slopes and its comprehension and prediction accuracy is important to properly develop soil conservation practices in forest areas. This process is largely influenced by sediment size, soil slope and water flow characteristics, but the results of the studies that have explored these influences are contrasting. This study has simulated in an experimental flume the rill detachment capacity (Dc) of soil with five particle sizes (0–0.25, 0.25–0.5, 0.5–1, 1–2, and 2–3 mm) at five water flow rates (0.26, 0.35, 0.45, 0.56, and 0.67 L m−1 s−1) and five bed slopes (3.5%, 9.1%, 19.2%, 29.1%, and 38.3%) on samples collected in a forestland of Northern Iran. Dc was significantly higher (by 70%) for sediments size over 1 mm compared to the other soil fractions and increased primarily with soil slope and secondarily with water depth. A modelling approach has shown that the unit stream power is the best predictor of Dc using power equations (NSE over 0.87). Linear regression models between Dc and shear stress (τ) were very accurate (r2 over 0.80 with few exceptions) in predicting both rill erodibility and critical shear stress, when developed separately for each particle size class. Sediments with size higher than 1 mm had lower resistance to rill erosion compared to the finer fractions.Overall, the study helps to better understand particle detachment of the erosion process, on which particle size is a key parameter. The modelling activity proposes to land planners values of the rill erodibility and critical shear stress of forested areas for applications in process-based erosion models.

RASING FORCES: PATTERNS OF REDISTRIBUTION OF POWER IN WORLD POLITICS

This article examines Rising Powers: Patterns of Power Redistribution in Global Politics, by creating a reliable framework for understanding the increasing complexities of the actors in the international arena. This is by studying the concept of power, which is one of the basic concepts in political science, whereby force imposes its logic on the curves of international relations and has multiple forms due to its complex nature. In what can be considered dual roles and reciprocal interactions, and to understand the dimensions, manifestations and nature of the actors in the power equation, especially the emergence of tensions and conflicts between the interests of the United States of America and the emerging powers in the world in light of the new strategic directions after the Cold War and each party's attempt to dominate areas of influence and wealth Proceeding from a pragmatic geopolitical policy.

Movement of Sediment Through a Burned Landscape: Sediment Volume Observations and Model Comparisons in the San Gabriel Mountains, California, USA

AbstractPost‐wildfire changes to hydrologic and geomorphic systems can lead to widespread sediment redistribution. Understanding how sediment moves through a watershed is crucial for assessing hazards, developing debris flow inundation models, engineering sediment retention solutions, and quantifying the role that disturbances play in landscape evolution. In this study, we used terrestrial and airborne lidar to measure sediment redistribution in the 2016 Fish Fire, in the San Gabriel Mountains in southern California, USA. The lidar areas are in two adjacent watersheds, at spatial scales of 900 m2 to 4 km2, respectively. Terrestrial lidar data were acquired prior to rainfall, and two subsequent surveys show erosional change after rainstorms. Two airborne lidar flights occurred (1) 7 months before, and (2) 14 months after the fire ignition, capturing the erosional effects after rainfall. We found hillslope erosion dominated the overall sediment budget in the first rainy season after wildfire. Only 7% of the total erosion came from the active channel bed and channel banks, and the remaining 93% of eroded sediment was derived from hillslopes. Within the channelized portion of the watershed erosion/deposition could be generally described with topographic metrics used in a stream power equation. Observed sediment volumes were compared with four empirical models and one process‐based model. We found that the best predictions of sediment volume were obtained from an empirical model developed in the same physiographic region. Moreover, this study showed that post‐wildfire erosion rates in the San Gabriel Mountains attain the same magnitude as millennial time scale bedrock erosion rates.

The Modeling of Power and Parameters on Wheel Hub for Motor in Forging Process

With the increasing diameter and stress the power applied to motor wheel may increase in proportional, which means the big power will be formed in forge process of motor. Furthermore with increasing height and rotation it may increase as well. So that through power equation to be established the properties may be designed and checked before made. Detail value is needed to calculate the hub power according to the curves between them. The stress of hub is the first factor to consider and then its diameter and height which is second factor. The bigger power is 12KW and 35KW when rotation is 10r/m and height is from 350mm to 150mm respectively. That means that in the scope of this field the power may be bigger enough. When continuing to incline height the power will no change. The time increases as diameter and height inclines. The time will incline as the rotation declines.

АНАЛИЗ ОТПРАВЛЕНИЯ ГРУЗОВ ВНУТРЕННИМ ВОДНЫМ ТРАНСПОРТОМ В РАЙОНЫ КРАЙНЕГО СЕВЕРА

The article presents an analysis of shipped goods by inland water transport and their forecast using the Trend Line program, which is included in the MS Excel database software. This analysis was based on statistical data for the period from 2015 to 2020 inclusive. The resulting equations showed that the forecast should use linear, logarithmic, exponential and power equations, on the basis of which the forecast was made until 2030. Key words: Northern delivery, shipped goods by inland water transport, analysis, forecast.

Non-conservative effects on spinning black holes from world-line effective field theory

We generalize the worldline EFT formalism developed in [4–9] to calculate the non-conservative tidal effects on spinning black holes in a long wavelength approximation that is valid to all orders in the magnitude of the spin. We present results for the rate of change of mass and angular momentum in a background field and find agreement with previous calculations obtained by different techniques. We also present new results for both the non-conservative equations of motion and power loss/gain for a binary inspiral, which start at 5PN and 2.5PN order respectively and manifest the Penrose process.

Л. Г. Раменский и аллометрия растений (история и современное состояние проблемы)

A historical review of the new direction of botanical science, namely, «plant allometry» was made. In this review, the attention is focused only on establishing the dependence of the aboveground mass of plants on their size. The first foreign experiments on the indirect determination of the aboveground mass of herbs, semishrub, and low shrub date back to the 1930s. Now the determination of the aboveground mass of these plants based on the re-sults of measuring their habitus has become widespread. In addition to height and cover, the volume of plants began to be used as predictors of aboveground biomass. Since the second half of the last century, power (expo-nential) equations have been used to estimate the aboveground mass of plants in hayfields and pastures from the results of measuring their habitus. By now, the "allometry of plants" has gone far beyond the limits, which reflect only the regularities connecting the sizes of plants with each other, as well as their size and productivity of plants. L. G. Ramensky began to conduct his experiments on the indirect determination of the aboveground mass of plants in hayfields and pastures much earlier than foreign researchers did. In 1915, he proposed the notion of "projective weight". This is the mass of plants per unit area of its cover. At first L. G. Ramensky assumed to calculate this value proceeding from the projective cover of plants. However, soon he became convinced that such a calculation gives a very unstable result. In 1938, L. G. Ramensky proposed to take into account the height of plants to determine the projective weight. He also proposed multiple linear regression equations to predict projective weight depending on the height of vegetative shoots and the ratio of the number of flower shoots to the cover of the plant. In the early 1950s, L. G. Ramensky summarized the accumulated material regarding the de-termination of the weight of the aboveground mass of individual plants by the parameters of their habitus. How-ever, this generalization was published only in 1966, 13 years after the death of L. G. Ramensky. Together with his colleagues, he calculated a special coefficient for many plants, reflecting the degree of dependence of the projective weight on the morphological, anatomical features of the species, as well as the conditions of their growth. Estimation of the aboveground mass of herbaceous plants, semishrub and low shrub based on the results of measuring their habitus that was started by Ramensky at the beginning of the last century, has outgrown the utilitarian need to determine feed reserves in hayfields and pastures. This assessment entered the framework of an independent direction of botanical science, which is currently called «plant allometry».