Power Equation Research Articles

Evaluation of body weight and color of cultured European catfish (Silurus glanis) and African catfish (Clarias gariepinus) using image analysis

Two cultured catfish species (European catfish Silurus glanis, and African catfish Clarias gariepinus) were evaluated for their weight estimation and colors by image analysis. A total of 60 whole fish from each species were first weighed, and then their pictures taken by a digital camera in a light box. Length, weight and color of all fish were determined by image analysis and results were compared between the two fish. Fish weight ranged from 7.4 to 39.61 g and 25.71 to 93.91 g for European and African catfish, respectively. Weight (W) vs length (L) data were fitted linear (W = A + BL), power (W = A LB) and second order polynomial equations (W = C0 + C1 L + C2 L2). The R2 values ranged from 0.835 to 0.974. For the W vs view area (V) relationship, the same equations were used. The R2 values for these equations ranged from 0.927 to 0.972. No significant difference was found between the average color values according to the L*, a* and b* distributions for both fish species (P > .05). Image analysis can easily determine length, view area, and color of fish and help in developing W vs L, and W vs V relationships.

Modeling comminution of iron ore concentrates in industrial-scale HPGR

High-pressure grinding rolls have an important role in several iron ore pellet feed preparation circuits. Modeling and simulation are potentially useful tools to improve their performance, but the applicability of mathematical models from the literature in this particular application has not yet been demonstrated, although the model by Torres and Casali has been identified as having good potential. The present work relies on several surveys on four HPGRs with variable diameters (1.4 to 2.25 m) and aspect ratios (0.88 to 1.45) operating in pelletizing plants to test the model originally proposed by Torres and Casali, as well as modifications proposed to it.Inadequacies have been found in the original model, which gave poor predictions of power, throughput and product size distribution along the roll's length. Modification of the power equation, incorporating a machine-dependent correction factor for the nip angle, as well as several modifications to the throughput model, including an expression meant to account for the ejection of material from the edge of the rolls and extrusion, resulted in very good agreement between data from surveys and the model. Finally, incorporation of an empirical correction equation to account for saturation and a more general expression for the roll profile led to good agreement between measured and predicted product size distributions, including their variation along the roll's length.

Research on magnetorheological elastomer forming process for complicated superalloy hollow part

In this paper, a magnetorheological elastomer (MRE) forming process is developed to form a complicated hollow part of GH4169 superalloy. The novel forming process can realize the differential loading of the forming pressure and avoid liquid leaking in the conventional hydraulic forming process. The principle of the MRE forming process can be illustrated as that the MRE will bulge under the effect of the applied magnetic field. Hence, the local forming pressure in the deformation zone of the part will increase during the forming process. To estimate the range of current and the axial displacement of the punch, a power equation based on power approach and electromagnetic theory is established. Numerical simulations and experiments study the deformation process and the die filling of tube blank under different magnetic field intensities. Response surface methodology (RSM) is used to determine the optimal process parameters. RSM also models the predicted equations of the maximum thinning ratio and the average bulging diameter. Besides, the fitted RSM model’s accuracy is quantified by a statistical method of analysis of variance. Finally, the predicted equations’ reliability and the optimal process parameters obtained by RSM are proved by a validated experiment.

Empowering Forest Owners with Simple Volume Equations for Poplar Plantations in the Órbigo River Basin (NW Spain)

Hybrid poplar plantations are becoming increasingly important as a source of income for farmers in northwestern Spain, as rural depopulation and farmers aging prevent landowners from planting other labor-intensive crops. However, plantation owners, usually elderly and without formal forestry background, lack of simple tools to estimate the size and volume of their plantations by themselves. Therefore, farmers are usually forced to rely on the estimates made by the timber companies that are buying their trees. With the objective of providing a simple, but empowering, tool for these forest owners, simple equations based only on diameter were developed to estimate individual tree volume for the Órbigo River basin. To do so, height and diameter growth were measured for 10 years (2009–2019) in 404 trees growing in three poplar plantations in Leon province. An average growth per tree of 1.66 cm year−1 in diameter, 1.52 m year−1 in height, and 0.03 m3 year−1 in volume was estimated, which translated into annual volume increment of 13.02 m3 ha−1 year−1. However, annual volume increment was different among plots due to their fertility, with two plots reaching maximum volume growth around 11 years since planting and another at 13 years, encompassing the typical productivity range in plantations in this region. Such data allowed developing simple but representative linear, polynomial and power equations to estimate volume explaining 93%–98% of the observed variability. Such equations can be easily implemented in any cellphone with a calculator, allowing forest owners to accurately estimate their timber existences by using only a regular measuring tape to measure tree diameter. However, models for height were less successful, explaining only 75%–76% of observed variance. Our approach to generate simplified volume equations has shown to be viable for poplar, but it could be applied to any species for which several volume equations are available.

Multi-parameter theoretical analysis of wearable energy harvesting backpacks for performance enhancement

Wearable energy harvesting technologies show a promising potential in IoT (Internet of Things) and human daily life because of their continuous power supply in place of traditional chemical batteries. However, the coupling effects between mechanical and electrical parameters, as well as human motion features, significantly complicate the performance of wearable energy harvesters. To address this issue, a multi-parameter theoretical analysis is conducted in this paper to improve the performance of an energy harvesting backpack composed of a spring, mass, electromagnetic motor, and rack-pinion-based power takeoff. The analytical equation of the average output power of the energy harvesting backpack is derived as a function of spring stiffness, external resistance, and structural and electrical damping. A comprehensive analytical analysis and numerical simulation are performed based on the average power equation to study the influence of carried mass and walking speed on the energy conversion performance. Experimental tests are implemented for different human subjects, various carried mass, spring stiffness, and electrical resistances to verify the analytical analysis. Theoretical and experimental results demonstrate that the optimal carried mass and external resistance for generating the maximum power output are determined by the total damping of the mechanical system and electrical circuit instead of resonance. Moreover, the sensitivity of power output to the human walking frequency and the carried mass can be reduced by sacrificing the peak output power. The results show that the optimal backpack with a carried mass of 12.95 kg can generate 4 W power at the walking speed of 5.6 km/h.

Size of National Assemblies: The Classic Derivation of the Cube-Root Law is Conceptually Flawed

For half a century, the analysis of the size of national assemblies was dominated by the famous cube-root relation with the population. However, a revisitation of that historical work with a physicist’s approach reveals basic conceptual problems that fatally undermine its conclusions. Furthermore, the assembly size evaluation exceeds the accuracy of all power equations, which cannot be reliably used for political analysis.

Image Analysis to Quantify Weight-length, Weight-area, and Change of Color of Three Commercial Mullidae Species during Cold Storage

ABSTRACT Image analysis was used to quantify weight-length, weight-area, and change of color for three fish caught in the Mediterranean (Red mullet Mullus barbatus, Por’s goatfish Upeneus pori, and goldband goatfish Upeneus moluccensis) during 7 days of storage at 4 ± 1°C. Length-weight data were fitted with a power equation. R2 ranged from 0.759 to 0.880. U. moluccensis showed an isometric growth, while the others had a negative allometric growth. For the view area (V)-weight relationship, linear and second order polynomial equations were also used in addition to the power equation. The R2 values for these ranged from 0.895 to 0.952. Average L*, b*, and ΔE values for all fish increased with storage time; but the a* values decreased (P < .05). The color change index (CCI) of the fish over storage time decreased, suggesting a smoothing of colors. Although its colors changed over time, the yellow band of the goldband goatfish did not change. Correlation of these computer-generated parameters using image analysis would allow quantitative evaluation of fish color with sensory analysis.

Effects of Shallow Water Table Depth on Vegetative Filter Strips Retarding Transport of Nonpoint Source Pollution in Controlled Flume Experiments

Vegetative filter strips (VFSs) have been recommended as the best management practice for reducing runoff nonpoint source (NPS) pollution. The efficiency of VFSs located adjacent to water bodies can vary with shallow water table depths (WTD). A vegetated soil tank containing silt loam soil and Shortleaf Lilyturf vegetation was designed to study the effects of VFSs under shallow WTD (0.08, 0.22, and 0.36 m) on retentions of surface runoff, sediment, phosphorus, and bromide. Experiments were conducted with a simulated rainfall intensity of 28 mm h−1 and inflow rates of 4.02–4.56 L min−1. The results revealed that a deep WTD, low grass spacing, and low slope had high VFS retention efficiencies. The retention efficiencies varied greatly from 35%, 70%, 64%, and 55% at the 0.08-m WTD in the experimental group with high grass spacing (6.69 cm) and low slope (5%) to 96%, 98%, 96%, and 95% at the 0.36-m WTD in the experimental group with low grass spacing (4.18 cm) and low slope (5%) for surface runoff, sediment, phosphorus, and bromide, respectively. A steeper slope (at the same grass spacing) increased the effects of the WTD on VFS performance. For each experimental group, the average surface runoff outflow rate decreased with the WTD, whereas the average subsurface lateral flow rate increased. The transport of phosphorus in the surface runoff almost resembled that of bromide, and the average concentration (C/C0 Ave) of phosphorus and bromide decreased with the WTD. For the subsurface lateral flow, the transport of bromide and phosphorus exhibited typical breakthrough behaviors during each experiment, and both the normalized phosphorus and bromide concentrations in increasing limbs could be described by power equations. The high concentration of pollutants in the subsurface lateral flow may have affected the adjacent water bodies and groundwater. In quantification of the impact of WTD on effectiveness of VFS, we can effectively control the NPS pollutants in a watershed.

Critical Nitrogen and Nutritive Index in Cultivars of Cenchrus purpureus (Schumach) Morrone

Objective: To determine and compare the parameters of the nitrogen curve and the nutritive nitrogen index of cultivars of Cenchrus purpureus with and without nitrogenous fertilization.Design/Methodology/Approach: Five cultivars of C. purpureus with or without fertilization were evaluated, and the dose was 141N-43P-20K. The grass was harvested every 21 d with production of dry matter (DM) and nitrogen (N). Growth rates and Critical Nitrogen (Nc) were obtained. The negative power equation with its parameters Nc and the Nitrogen Decrease Coefficient (Cd) were used. The Nutritive Nitrogen Index (NNI) was obtained with the Nc parameter of each curve, divided by the N content of the cultivar in each sampling. The data were analyzed with a completely randomized design in a factorial arrangement of five (cultivars) and two levels of fertilization. Results: Nc of 2.6 and a Cd of 0.65 fertilized, and 1.14 of Nc and 0.68 of Cd without fertilization, and in turn all of them supplemented the amount of N for their growth from soil. The NNI was 0.8 for the fertilized cultivars, with classification of excess and sufficient for the first 56 d. Study Limitations/Implications: Variables to determine the availability of water and the balance of soil-plant N could further expand the knowledge of these tools. Findings/Conclusions: Parameters obtained such as Nc and NNI help to determine nutritional status of the fodders.

New closed-form estimators for weighted Lindley distribution

We propose new closed-form estimators for two-parameter weighted Lindley (WL) distribution. These new estimators are derived from likelihood equations of power transformed WL distribution. They behave very similarly to maximum likelihood estimators (MLEs) and achieve consistency and asymptotic normality. Numerical results show that, unlike existing closed-form estimators, the new estimators are uniformly comparable to MLEs. In addition, to reduce biases of the new estimators in the case of small samples, we apply a bias-correction method to the new estimators, based on the approximate Cox-Snell formula. Our simulation studies indicate that this bias-correction method is effective in enhancing small-sample performance. Finally, we present three real data examples.

Thin-Layer Drying Characteristics of Fresh and Sun-Dried Buckwheat Hay

Highlights Thin-layer drying of fresh and sun-dried buckwheat hay was studied at 30°C to 180°C and 12.5% to 60% relative humidities. Buckwheat hay drying occurred in the falling-rate period. Partial sun-drying of the hay could reduce drying time by 50%. The D eff values of fresh flowers, leaves, and stems ranged from 1.4×10 -10 to 60×10 -10 m 2 /s. Abstract. Thin-layer drying characteristics of fresh and sun-dried buckwheat hay were studied at 30°C to 180°C, 12.5 to 60% relative humidities, and 0.2 m/s constant air velocity. The hay was harvested on three different times with a 10 to 12 d interval between the harvesting times. Half of the harvested hay was sun-dried on the field for 4 d (referred to as sun-dried hay). The drying behavior of flowers, leaves, and stems of the fresh and sun-dried hay was characterized. Moisture content of the fresh buckwheat flower was 0.777 to 1.633 (decimal dry basis), and fresh stems had a maximum moisture content of 5.64. Moisture content of the fresh hay decreased with the increase of growth time. Sun-drying on field could decrease more than half of the moisture content of the harvested fresh hay. Flowers, leaves, and stems needed varying drying times to reach their equilibrium moisture contents. The order of the drying time from the fastest to the slowest was flowers, leaves, then stems. Sun-dried and later harvested hay needed less drying time. The logarithmic model was the best fit for all drying processes of the flowers, leaves, and stems at different harvesting times and drying conditions. The effective moisture diffusivity of both fresh and sun-dried hay ranged from 1.4×10-10 to 60× 10-10 m2/s depending on different experimental conditions. The activation energy of the hay was from 21.08 to 33.85 kJ/mol. A power equation was the best equation to describe the drying constant of hay with their drying temperature. Keywords: Activation energy, Combination drying, Hay drying, Thin-layer drying, Water diffusivity.

Влияние параметров среды на выходную мощность ветроэлектрической части энергокомплекса на базе ВИЭ

The wind speed has the greatest influence on the power flow, since it is included in the power equation in the third degree. It is impossible to ignore the presence in the equation of the air density, which is affected by its temperature, pressure and humidity. The air density is most often chosen according to the conditions of the standard atmosphere. The concept of a standard atmosphere varies from source to source and depends on the field of study. (Research purpose) The research purpose is in studying the influence of temperature, pressure and humidity on the power of the wind flow. (Materials and methods) The article presents existing works on the effect of air density on the operation of wind turbines. Authors selected sources that use the parameters available for measurement, for which there is statistical meteorological data. The study uses the temperature, pressure and relative humidity of the air as data with extensive meteorological observations. (Results and discussion) The article considers the influence of each of the factors depending on the levels of the other factors. The temperature change from -40 to +60 degrees Celsius at low pressure gives a deviation spread of 36.43 percent, while at high pressure this spread is 39.42 percent. A similar situation is observed with pressure, the influence of which varies in the range of 6.97-9.96 percent. The most unfavorable combination of factors (high pressure, low temperature and humidity versus low pressure, high temperature and humidity demonstrated an effect of up to 46.39 percent. (Conclusions) Temperature has the greatest impact on air density and power flow, and humidity has almost no effect on air density and power flow. With the most unfavorable combination of factors, the power flow through the wind wheel can decrease almost to one and a half times while maintaining its speed. The influence of air temperature cannot be ignored when calculating the power of the wind flow.

Allometric equations for estimating aboveground biomass of khat (Catha edulis)-stimulate grown in agroforestry of Raya Valley, Northern Ethiopia

Khat plant (Catha edulis Forsk) is an evergreen perennial cash crop cultivated in east Africa, southwest Arabia, and Madagascar. The plant is known for its production of stimulant fresh leaves, and expanding as expense of other land uses for its short-term financial returns. We, therefore, developed allometric equations for estimating aboveground biomass and carbon (C) removal of khat grown in farmlands of Raya Valley, Northern Ethiopia. A total of 31 plant individuals were harvested destructively on the basis of their diameters and age ranges. The equations were parametrized using biometric variables such as basal diameter (d10), diameter at breast height (d), dominate height (doh) and mean height (h). Results of the analysis showed that, stem accounted for 58%, branch 32% and foliage 10% of the aboveground biomass (AGB). Commercial foliage biomass C removal ranged from 2.3 to 2.7 Mg ha−1. The power equation, AGB = b1×d10b2×dohb3, was the best (highest ranked using goodness-of-fit statistics), explaining 96% of the variation in aboveground biomass (p < 0.01). Models comparisons showed that our best ranked equation (M6) improved the aboveground biomass estimate by 44% and 48 % that of generic and other species-site specific equations developed in the tropics, respectively. Thus, our best species-site specific equation developed in this study can accurately estimate aboveground of khat plant biomass in the study region.

ACOUSTIC MODELS OF THE MAIN SOURCES OF NOISE OF MULTI-SPINDLE DRILLING WOODWORKING MACHINE

The harmful factors in the woodworking industry include the increased noise level in the workplace. This is especially true when working with multi-spindle drilling woodworking machines. The main sources of noise include the constant speed of drills, the geometric shape of the motor and the body of the cutting units, as well as the pneumatic feed mechanism of the cutting units or workpieces. The article presents a theoretical justification of noise sources, which allowed us to obtain the equation of sound power of noise sources in general form. The acoustic calculation of the main noise sources was performed using the obtained formulas. The obtained acoustic models of the main noise sources showed that the practical calculation of sound pressure levels or sound power is actually reduced to determining the vibration rates on the natural vibration forms of the sources.

Analysis and Control of Modular Multilevel Matrix Converters under Branch Fault Conditions

The modular multilevel matrix converter (M3C) is a promising topology for high-voltage and high-power direct ac-to-ac power conversion applications. Fault tolerance ability is one of the advantages of the M3C. To further enhance the reliability of the M3C, this article proposes a novel branch current configuration method for branch fault conditions, which is available either one or two branches are failed. By deriving basic branch current configurations and analyzing branch dc power equations under branch fault conditions, feasible branch current configurations can be directly derived. In terms of minimizing the maximum peak branch current, the derived configuration is also the optimal one for the single branch fault condition. Compared with the existing method, the proposed method does not need to solve configuration coefficients of branch currents offline, which is automatically adaptive to different load conditions. An M3C prototype with three submodules each branch is built, and experimental results are presented to validate the proposed branch fault tolerance method.

Comparison of sediment rating curves and sediment yield in subbasins of the Itacaiúnas River Watershed, Eastern Amazon

ABSTRACT Understanding the hydrosedimentological dynamics of tropical rivers is a challenge in the Amazon due to its remote and difficult-to-access areas. This study was based on data collected from 16 hydrosedimentological control sections in the 6 subbasins that make up the Itacaiúnas River Watershed (IRW), with 4 annual campaigns (high water levels, rising water levels, falling water levels, low water levels) between 2015 and 2019, with the aim of constructing and comparing sediment rating curves and sediment yield. The data at the mouth of the IRW revealed that the rainy season is responsible for 93% of liquid discharges (Q) with an average of 1460.88 m3/s and for 98% of suspended sediment discharges (SSQ) with an average of 5864.15 tons/day. Suspended sediment concentrations (SSCs) are low to moderate (50 to 150 mg/l). The curves encompassing all the data showed R2 values (0.92 to 0.99) greater than the curves with only the values of the rainy or dry season, indicating a good fit of the power equation to the SSQ and Q data for all sections studied. Higher values of coefficients a and b show areas of greater sediment production and deforestation, as well as areas with new sources of sediment and preserved forest.

Morphometry and Relative Growth of Ophiolepis crassa (Echinodermata: Ophiuroidea), a Brittle Star from the Eastern Pacific.

Tropical ophiuroid fauna belonging to the family Ophiolepididae are almost unknown. This study deals with the relative growth and morphometric traits of the ophiuroid Ophiolepis crassa from the Gulf of California, Mexico. Specimens examined in this study came from the Colección Nacional de Equinodermos, Universidad Nacional Autónoma de México, and were collected over soft bottoms off Punta Gorda. Thirteen anatomical features were measured in a total of 152 specimens, including disk diameter, arm length, as well as length and width of dorsal and ventral arm plates, and radial, oral, and adoral shields. Based on the range of values of the disk diameter, varying from 4 to 19 mm, we provided quantitative data on each anatomical measurement considering three size classes. Morphometric data were adjusted to a power equation to detect the degree of allometry in the growth of anatomical traits. Results indicated that all the ventral and dorsal plates, as well as the radial, oral, and adoral shields, suffer changes in shape during growth, but these changes are stronger in the plates. In addition, an analysis of symmetry applied to both right and left radial shields revealed that these structures remain nearly symmetrical during growth. The disk diameter vs arm/disk relationship indicated that the species is a surface dweller inhabitant of the seafloor. This study, based on a single sample collected in a restricted area of the eastern Pacific, provides useful quantitative information for further taxonomic, systematic, or biogeographic studies.

Mathematical model for calculating the reliability of the characteristics of the designed trailer frame

The article looks through the justification of the projected frame reliability characteristics of the trailer and its components. Given the desired level of reliability for the frame as a whole promoted calculation of the required parameters of reliability, including the probability of failure-free operation and mean time between failure elements of the trailer frame. The substantiation of indicators of reliability and durability of the projected trailer frame is carried out. Based on the calculation of the complexity factors of the frame elements, the required reliability indicators were calculated, including the probability of non-failure operating (PNFO) and the mean time between failures (MTBF). To assess the frame's durability, the formula has been proposed with the correction coefficient εc, which can be used to calculate the resource of trailer frames made of elements of rolled steel of various grades. A mathematical model for evaluating the durability of the trailer frame is also proposed, based on the Weibull distribution and the power equation of the fatigue curve. A specific example shows the adequacy of the proposed formula to experimental values (The deviation from the experimental values of The Central Scientific Research Automobile and Automotive Engines Institute “NAMI” is 9 %).

Kompensacja reaktancyjna odbiornika liniowego w układach trójfazowych czteroprzewodowych zasilanych napięciem sinusoidalnym asymetrycznym w myśl teorii składowych fizycznych prądu (część 2)

Four-wire systems are the most common ones in everyday life. Electrical installations within the home, office, or industrial plant are mostly four-wire installations. Receivers connected to such a system are mainly single-phase loads, which from the power connection are an unbalanced three-phase load. Apart from, the load imbalance, the supply voltage also has some asymmetry. Voltage asymmetry, load imbalance, the design of reactance compensators are issues that were not simultaneously included in the power equation in fourwire systems. This article presents the mathematical fundamentals of the construction of reactance compensators operating in voltage asymmetry.

Modelling nitrogen, phosphorus, potassium, calcium and magnesium uptake, and uptake concentration, of greenhouse tomato with the VegSyst model

The existing version of the VegSyst model (V2) simulates daily dry matter production (DMP), crop evapotranspiration (ETc) and crop N uptake of tomato and other vegetable crops grown in greenhouse in SE Spain. In this study with greenhouse tomato, (i) the VegSyst model was adapted to simulate daily values of seasonal (i.e. throughout the crop) uptake of K, P, Ca and Mg, (ii) the simulation of seasonal N, K, P, Ca and Mg uptake was validated, and (iii) the simulation of seasonal uptake concentration (UC) of N, K, P, Ca and Mg was validated. For K, P, Ca and Mg, dilution curves (i.e. relationship of crop content of the nutrient (%) to DMP) were obtained from pooled data of six treatments from two greenhouse tomato crops. These relationships were all described by power equations with R2 values of 0.72–0.92 for all nutrients, except Mg that had a R2 of 0.40. For the simulation of tomato crop N uptake, the dilution curve previously used in V2 was replaced by the critical N curve for tomato of Padilla et al. (2015). The simulation of uptake of N, K, P, Ca and Mg was validated with a spring, soil-grown, long-life type, tomato crop (Tomato-11) and two long season soilless cherry tomato crops (Cherry-16 and Cherry-17). Seasonal uptake of N, K, P and Ca was adequately simulated in the three validation crops, with best performance (Relative Error (RE) ≤0.2) in the Cherry-17 crop. In the three validation crops, modelling of Mg uptake had poor performance. For simulation of UC in the two cherry tomato crops, there was good performance for N, K, P and Ca in Cherry-17, and reasonable to good performance in Cherry-16. The simulation of the UC for Mg was poor. The revised VegSyst model, identified as V3, will be incorporated into a decision support system (DSS) to provide recommendations for nutrient solution composition for soil-grown and soilless tomato crops grown in greenhouses.