Artykuły w czasopismach na temat „Variable load conditions”
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1
Almeida, K. C., i R. Salgado. "Optimal power flow solutions under variable load conditions". IEEE Transactions on Power Systems 15, nr 4 (2000): 1204–11. http://dx.doi.org/10.1109/59.898091.
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SHAO, Yimin. "Gearbox Deterioration Detection under Steady State, Variable Load, and Variable Speed Conditions". Chinese Journal of Mechanical Engineering 22, nr 02 (2009): 256. http://dx.doi.org/10.3901/cjme.2009.02.256.
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Zhao, Haoyang. "Classical PID Control of A Quadcopter UAV Under Variable Load Conditions". Academic Journal of Science and Technology 9, nr 2 (23.02.2024): 44–46. http://dx.doi.org/10.54097/13m5xg10.
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In recent years, the application of UAVs has become more and more extensive, resulting in a number of special operation UAVs. Quadrotor aerial robots have become one of the most popular vehicles at home and abroad because of their small size, light weight, simple structure, low cost, low requirements for takeoff and landing, and good maneuverability. UAVs are required to perform different tasks in the current complex environment, so variable loads are inevitable, and the stability of the UAV body is especially important when performing variable loads, and there are many ways to help and verify the attitude of the UAV during flight. In this paper, in order to more intuitively see the self-generated stability of the UAV under variable load conditions, the dynamics model of the UAV will be established first, and the simulation results show that the movement of the UAV has a very good stability. However, in the previous research, it is not possible to visualize the stability and flight state of the UAV when it is flying under variable load, this paper will make the UAV keep its own flight stability under two kinds of loads through the PID design model. At the same time, the function of the UAV's own mass change during flight is found, and the design function is used to show the stability curve of the UAV when it flies with its own changing mass. Through the final simulation and calculation, the experiment found that through the PID control, the flight state of the UAV when flying with variable load can be observed more intuitively, and the stability state of the UAV when flying can also be observed.
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Lukasik, Konstanty, Jerome Cheron, Gustavo Avolio, Arkadiusz Lewandowski, Dylan F. Williams, Wojciech Wiatr i Dominique M. M. P. Schreurs. "Uncertainty in Large-Signal Measurements Under Variable Load Conditions". IEEE Transactions on Microwave Theory and Techniques 68, nr 8 (sierpień 2020): 3532–46. http://dx.doi.org/10.1109/tmtt.2020.2995618.
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Pollock, H. "Simple constant frequency constant current load-resonant power supply under variable load conditions". Electronics Letters 33, nr 18 (1997): 1505. http://dx.doi.org/10.1049/el:19971063.
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Alwadie, Abdullah. "A Real Time Condition Monitoring System for Gears Operating under Variable Load Conditions". Indonesian Journal of Electrical Engineering and Computer Science 9, nr 2 (1.02.2018): 493. http://dx.doi.org/10.11591/ijeecs.v9.i2.pp493-501.
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Gears are important component of the rotational power transmission system and are largely used in variable load and speed applications. The faults on the gear generate excessive vibration which leads to breakdown of the machine. Sensor based methods could diagnose gear faults but proved to be expensive and have limited applications due to heavy cost and need of access of gear box for sensor installation. The motor stator current analysis has been reported to overcome the drawbacks of the sensor based fault detection methods. However, motor stator current analysis has a limited capability for reliable detection of small gear fault signatures typically for low load conditions. This paper presents an alternative non-invasive approach based on instantaneous power analysis of the motor to reliably diagnose gear faults for variable load applications. The theoretical and experimental results indicates that the instantaneous power analysis offers three fault related harmonics and amplitude variations on these harmonics could give the indication of health status of the gear.<strong> </strong> The superiority of the proposed instantaneous power analysis technique has been confirmed through experiments performed on three operating points of the motor. The comparison of the amplitude sensitivity of the motor stator current and instantaneous power at three operating points has been performed to validate the superiority of the proposed technique.
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Gao, Changlun, Junliang Huo, Zhantong Li, Beihuo Yao, Zhaokai He, Fangren Zhang, Shunli Sun i Weibin Wu. "Research and Development of Gearbox Load Spectrum Database under Variable Working Conditions". International Journal of Emerging Technology and Advanced Engineering 11, nr 10 (15.10.2021): 29–39. http://dx.doi.org/10.46338/ijetae1021_04.
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Gearbox load spectrum is the data basis for gearbox fatigue life prediction and strength verification. As the amount of load spectrum data increases exponentially and the demand for sharing increases, it is necessary to introduce database technology to store and manage load spectrum data. In this paper, the collection and processing of load data and the compilation of load spectrum are introduced in turns firstly. Then it sums the development and research status of database technology and the technical route of combining load spectrum database up secondly. Moreover, the current status of load spectrum database and the design steps of load spectrum database are summarized. Finally, the development trend of load spectrum database research is generalized and the prospect is put forward.
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Chen, Chong Liang, Li Guo Liu i Zi Feng Ni. "The Wear Mechanism of DLC Films at Variable Working Conditions". Advanced Materials Research 199-200 (luty 2011): 683–88. http://dx.doi.org/10.4028/www.scientific.net/amr.199-200.683.
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The Diamond-like carbon coating (DLC) was derived by the PVCD method on the 45 steel surfaces. The frictional properties and fatigue failure of 45 steel with the DLC films were investigated under three different conditions including full contact condition, horizontal reciprocating movements and vertical reciprocating movements. It was found that (a) at full contact conditions: the increase in the load leads to the initial decrease in the frictional coefficient and then increase, and a lowest frictional coefficient of 0.205 appears at 250N; (b) at horizontal reciprocating conditions: the slow decrease in the frictional coefficient was caused by the increase in load, and frictional coefficients of 0.213 and 0.178 appears at 100N and 300N, respectively; (c) at vertical reciprocating conditions: the frictional coefficient was initially enhanced and then followed by a decrease trend; the highest frictional coefficients of 0.640 appears at load of 200N. The wear rate was slightly enhanced as the load is lower than 200N, and was sharply increased with the further increase in the load. The lowest wear rate was 1.55 mg/10000r, and the highest wear rate was 15.6mg/10000r.
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Akhtulov, A. L., O. M. Kirasirov i M. O. Kirasirov. "Features of calculation of steel structures of bridge cranes at variable loads". MATEC Web of Conferences 298 (2019): 00032. http://dx.doi.org/10.1051/matecconf/201929800032.
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The article deals with the calculation of metal bridge cranes operating under the influence of variable loads. Requirements to static and dynamic characteristics of mechanisms of load-lifting cranes are caused by specifics of work, features of a design and operating conditions of the cranes working at variable loadings. Thus, it is proposed to perform calculations of parts of crane mechanisms for endurance, operating under non-stationary variable load, based on the principle of linear summation of damage, allowing the calculation from the point of view of the load equivalent to the entire range of operating loads.
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Liu, Haigang, Chu Sun, Mengyu He, Na Wang i Yuanjun Zhou. "Analysis of Synchronous Generator Self-Excitation under Capacitive Load Condition in Variable-Frequency Aviation Power System". Machines 11, nr 1 (23.12.2022): 15. http://dx.doi.org/10.3390/machines11010015.
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As power electronic converters become more widely used in aviation power systems, the associated capacitive loads in the harmonic filter circuits increase accordingly. The risk of self-excitation of aeronautical synchronous generators due to capacitive loads is thus increased. Compared with the self-excitation of a generator in a conventional fixed-frequency power system, this process is more complicated in a variable-frequency aviation power supply (360–800 Hz), as both the varied frequency and the loading conditions contribute to the self-excitation. To quantify this effect, in our study, a series-parallel model of simplified RLC loads under a variable-frequency power supply was built. The criterion of generator self-excitation, given in terms of the generator impedance and the load impedance, was then derived. To facilitate the load configuration design in the case of an aviation power system, a comprehensive analysis of the influences of the varied load power and system frequency on the load impedance was conducted. A graphical approach was proposed to determine self-excitation by comparing the series load reactance and resistor with three critical impedances corresponding to three self-excitation criteria, which is more intuitive and enables one to visualize the tendency of self-excitation with varied frequencies and loading conditions more effectively. Finally, the influence of variable frequency on the self-excitation of the aeronautical synchronous generator was verified by the simulation results.
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Shneen, Salam Waley, Hashmia S. Dakheel i Zainab B. Abdullah. "Design and Implementation of No Load, Constant and Variable Load for DC Servo Motor". Journal of Robotics and Control (JRC) 4, nr 3 (10.05.2023): 323–29. http://dx.doi.org/10.18196/jrc.v4i3.17387.
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Simulations were conducted to improve and design an appropriate control system and obtain a model with the required development to suit the operation of the engine with constant and variable loads, which are the proposed working conditions that are suitable for many applications. The current simulation aims to build and design a model for an electric motor (DC Servo motor) and a model for a conventional controller (PID). The proposed model addresses the cases of fixed and variable loads in terms of using the controller that improves the performance of the motor’s work for different conditions. Three cases were developed to conduct the proposed tests, which included the case of no-load, fixed and variable load. Tests were conducted. Without the console and for the purpose of comparison and observation of improvement, the test was conducted with the addition of the console. The results showed system performance may improve depending on usage using traditional control systems. Performance measurement criteria are adopted for the purpose of comparison and observation of performance improvement. The criteria that are adopted are rise time and stability (steady state) in addition to the ratio of the rate of under and over-shoot. Where it can be deduced from this the possibility of using different control systems, including traditional ones, to improve performance, and they include controlling the speed of the motors, as well as controlling the effort, and the consequent effects on the subject of the study, as it deals with transient cases and changing operating conditions with more than acceptable efficiency and relatively high quality. There are four state simulation include, 1st at no load without controller: rise time equal 309.886ms , overshoot equal 44.203% and undershoot equal 9.597%.2nd at load without controller: rise time equal 216.319ms , overshoot equal 58.654% and undershoot equal 0.210%.3rd at no load with PID controller: rise time equal 1.177s , overshoot equal 0.505% and undershoot equal 1.914%.4th at load with PID controller: rise time equal 1.112s , overshoot equal 0.509% and undershoot equal 5.856%.
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Thorburn, Lukas P., Lynn S. Adler, Rebecca E. Irwin i Evan C. Palmer-Young. "Variable effects of nicotine and anabasine on parasitized bumble bees". F1000Research 4 (21.09.2015): 880. http://dx.doi.org/10.12688/f1000research.6870.1.
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Secondary metabolites in floral nectar have been shown to reduce parasite load in two common bumble bee species. Previous studies on the effects of nectar secondary metabolites on parasitized bees have focused on single compounds in isolation; however, in nature, bees are simultaneously exposed to multiple compounds. We tested for synergistic effects of two alkaloids found in the nectar of Nicotiana spp. plants, nicotine and anabasine, on parasite load and mortality in bumble bees (Bombus impatiens) infected with the intestinal parasite Crithidia bombi. Adult worker bees inoculated with C. bombi were fed nicotine and anabasine diet treatments in a factorial design, resulting in four nectar treatment combinations: 2 ppm nicotine, 5 ppm anabasine, 2ppm nicotine and 5 ppm anabasine together, or a control alkaloid-free solution. We conducted the experiment twice: first, with bees incubated under variable environmental conditions (‘Variable’; temperatures varied from 10-35°C); and second, under carefully controlled environmental conditions (‘Controlled’; 27°C incubator, constant darkness). In ‘Variable’, each alkaloid alone significantly decreased parasite loads, but this effect was not realized with the alkaloids in combination, suggesting an antagonistic interaction. Nicotine but not anabasine significantly increased mortality, and the two compounds had no interactive effects on mortality. In ‘Controlled’, nicotine significantly increased parasite loads, the opposite of its effect in ‘Variable’. While not significant, the relationship between anabasine and parasite loads was also positive. Interactive effects between the two alkaloids on parasite load were non-significant, but the pattern of antagonistic interaction was similar to that in the variable experiment. Neither alkaloid, nor their interaction, significantly affected mortality under controlled conditions. Our results do not indicate synergy between Nicotiana nectar alkaloids; however, they do suggest a complex interaction between secondary metabolites, parasites, and environmental variables, in which secondary metabolites can be either toxic or medicinal depending on context.
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Glyva, V., O. Tykhenko, L. Levchenko i V. Kolumbet. "Сontrol of electromagnetic field levels under conditions of variable energy load". Scientific papers of Donetsk National Technical University”. Series: “Computer engineering and automation” 32, nr 1 (2019): 27–36. http://dx.doi.org/10.31474/2075-4272-2019-1-32-27-36.
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Lozano, Miguel A., Monica Carvalho i Luis M. Serra. "Allocation of economic costs in trigeneration systems at variable load conditions". Energy and Buildings 43, nr 10 (październik 2011): 2869–81. http://dx.doi.org/10.1016/j.enbuild.2011.07.002.
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Randall, R. B. "Vibration-based diagnostics of gearboxes under variable speed and load conditions". Meccanica 51, nr 12 (16.11.2016): 3227–39. http://dx.doi.org/10.1007/s11012-016-0583-z.
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Han, Qinkai, Xinglin Li i Fulei Chu. "Skidding behavior of cylindrical roller bearings under time-variable load conditions". International Journal of Mechanical Sciences 135 (styczeń 2018): 203–14. http://dx.doi.org/10.1016/j.ijmecsci.2017.11.013.
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Ren, Guo Quan, Wen Chen Zhang i Ben Li. "Research on the Gearbox Fault Signal Relation to the Sensitivity of Variable Working Conditions". Applied Mechanics and Materials 494-495 (luty 2014): 921–24. http://dx.doi.org/10.4028/www.scientific.net/amm.494-495.921.
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Established the gearbox fault model and simulated it at different load conditions view of the problem with gearbox experimental technique research under the variable speed and load conditions. The law between the changes of rotational speed and load with the system vibration signals was investigated and the corresponding optimal test fault condition was given. Based on this, validated the feasibility on fault diagnosis by increasing (decreasing) speed signal and found that the different load will have a different influence on the different fault signal. The different diagnostic purpose should be considered to design load conditions.
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Thorburn, Lukas P., Lynn S. Adler, Rebecca E. Irwin i Evan C. Palmer-Young. "Variable effects of nicotine, anabasine, and their interactions on parasitized bumble bees". F1000Research 4 (16.12.2015): 880. http://dx.doi.org/10.12688/f1000research.6870.2.
Pełny tekst źródłaStreszczenie:
Secondary metabolites in floral nectar have been shown to reduce parasite load in two common bumble bee species. Previous studies on the effects of nectar secondary metabolites on parasitized bees have focused on single compounds in isolation; however, in nature, bees are simultaneously exposed to multiple compounds. We tested for interactions between the effects of two alkaloids found in the nectar of Nicotiana spp. plants, nicotine and anabasine, on parasite load and mortality in bumble bees (Bombus impatiens) infected with the intestinal parasite Crithidia bombi. Adult worker bees inoculated with C. bombi were fed nicotine and anabasine diet treatments in a factorial design, resulting in four nectar treatment combinations: 2 ppm nicotine, 5 ppm anabasine, 2ppm nicotine and 5 ppm anabasine together, or a control alkaloid-free solution. We conducted the experiment twice: first, with bees incubated under variable environmental conditions (‘Variable’; temperatures varied from 10-35°C with ambient lighting); and second, under carefully controlled environmental conditions (‘Stable’; 27°C incubator, constant darkness). In ‘Variable’, each alkaloid alone significantly decreased parasite loads, but this effect was not realized with the alkaloids in combination, suggesting an antagonistic interaction. Nicotine but not anabasine significantly increased mortality, and the two compounds had no interactive effects on mortality. In ‘Stable’, nicotine significantly increased parasite loads, the opposite of its effect in ‘Variable’. While not significant, the relationship between anabasine and parasite loads was also positive. Interactive effects between the two alkaloids on parasite load were non-significant, but the pattern of antagonistic interaction was similar to that in the variable experiment. Neither alkaloid, nor their interaction, significantly affected mortality under controlled conditions. Our results do not indicate synergy between Nicotiana nectar alkaloids; however, they do suggest a complex interaction between secondary metabolites, parasites, and environmental variables, in which secondary metabolites can be either toxic or medicinal depending on context.
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Chen, Qingqiang, Yalei Yu, Jie Sun, Cainian Jing, Yanhua Zhao i Jia Wang. "Investigation of the Wear Behavior of Surface Welding AZ91 and AZ91+Gd Alloys under Variable Loading Conditions". Crystals 11, nr 5 (16.05.2021): 554. http://dx.doi.org/10.3390/cryst11050554.
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Adding rare earth elements to magnesium alloys is an effective way to improve their wear resistance. However, the effect achieved is closely related to the friction condition. In this paper, two different types of welding wires, AZ91 magnesium alloy and AZ91 + gadolinium (Gd), were used for surface welding. Dry sliding friction and wear experiments were performed on the surfacing alloys using the pin-on-disc test. The effects of Gd addition on the wear resistance and wear mechanism of the alloy were systematically studied under low to high loads. The results show that as the load increases, the friction coefficient of the surfacing AZ91 alloy gradually decreases as the wear rate increases. A mild–severe wear transition occurred at 100 N. The addition of Gd only slightly increased the wear rate under a load of 15 N. The wear rate was significantly decreased with loads in the range of 30 to 100 N and mild–severe wear transition was avoided. The influence of both Gd addition and load on the wear mechanism were considered. The overall wear resistance of the surfacing magnesium alloy was determined.
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Naz, R., i F. M. Mahomed. "Dynamic Euler-Bernoulli Beam Equation: Classification and Reductions". Mathematical Problems in Engineering 2015 (2015): 1–7. http://dx.doi.org/10.1155/2015/520491.
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We study a dynamic fourth-order Euler-Bernoulli partial differential equation having a constant elastic modulus and area moment of inertia, a variable lineal mass densityg(x), and the applied load denoted byf(u), a function of transverse displacementu(t,x). The complete Lie group classification is obtained for different forms of the variable lineal mass densityg(x)and applied loadf(u). The equivalence transformations are constructed to simplify the determining equations for the symmetries. The principal algebra is one-dimensional and it extends to two- and three-dimensional algebras for an arbitrary applied load, general power-law, exponential, and log type of applied loads for different forms ofg(x). For the linear applied load case, we obtain an infinite-dimensional Lie algebra. We recover the Lie symmetry classification results discussed in the literature wheng(x)is constant with variable applied loadf(u). For the general power-law and exponential case the group invariant solutions are derived. The similarity transformations reduce the fourth-order partial differential equation to a fourth-order ordinary differential equation. For the power-law applied load case a compatible initial-boundary value problem for the clamped and free end beam cases is formulated. We deduce the fourth-order ordinary differential equation with appropriate initial and boundary conditions.
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Arranz, Sofía, Abdolrasoul Sohouli i Afzal Suleman. "Buckling Optimization of Variable Stiffness Composite Panels for Curvilinear Fibers and Grid Stiffeners". Journal of Composites Science 5, nr 12 (15.12.2021): 324. http://dx.doi.org/10.3390/jcs5120324.
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Automated Fiber Placement (AFP) machines can manufacture composite panels with curvilinear fibers. In this article, the critical buckling load of grid-stiffened curvilinear fiber composite panels is maximized using a genetic algorithm. The skin is composed of layers in which the fiber orientation varies along one spatial direction. The design variables are the fiber orientation of the panel for each layer and the stiffener layout. Manufacturing constraints in terms of maximum curvature allowable by the AFP machine are imposed for both skin and stiffener fibers. The effect of manufacturing-induced gaps in the laminates is also incorporated. The finite element method is used to perform the buckling analyses. The panels are subjected to in-plane compressive and shear loads under several boundary conditions. Optimization results show that the percentage difference in the buckling load between curvilinear and straight fiber panels depends on the load case and boundary conditions.
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Martinez, Fredy, Holman Montiel i Fernando Martinez. "Fuzzy control of synchronous buck converters utilizing fuzzy inference system for renewable energy applications". International Journal of Electrical and Computer Engineering (IJECE) 13, nr 5 (1.10.2023): 5076. http://dx.doi.org/10.11591/ijece.v13i5.pp5076-5090.
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<p>In the present research, an innovative fuzzy control approach is developed specifically for synchronous buck converters utilized in renewable energy applications. The proposed control strategy effectively manages load changes, nonlinear loads, and input voltage variations while improving both stability and transient response. The method employs a fuzzy inference system (FIS) that integrates adaptive control, feedforward control, and multivariable control to guarantee optimal performance under a wide range of operating conditions. The design of the control scheme involves formulating a rule base connecting input variables to an output variable, which signifies the duty cycle of the switching signal. The rule base is configured to dynamically modify control rules and membership functions in accordance with load conditions, input voltage fluctuations, and other contributing factors. The performance of the control scheme is evaluated in comparison to conventional techniques, such as proportional integral derivative (PID) control. Results indicate that the advanced fuzzy control approach surpasses traditional methods in terms of voltage regulation, stability, and transient response, particularly when faced with variable load conditions and input voltage changes. As a result, this control scheme is highly compatible with renewable energy systems, encompassing solar and wind power installations where input voltage and load conditions may experience considerable fluctuations. This research highlights the potential of the proposed fuzzy control approach to significantly enhance the performance and reliability of renewable energy systems.</p>
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Sivakumar, P., i Arumugam Rajapandiyan. "Enhanced OPF for DG Penetrated Power System Network under Variable Load Conditions". Advanced Materials Research 984-985 (lipiec 2014): 1301–5. http://dx.doi.org/10.4028/www.scientific.net/amr.984-985.1301.
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In modern power systems, distributed generation turns out to be progressively significant. Conversely, the growing utilize of distributed generators origins the concerns on the growing system hazard owing to their probable breakdown or unruly power productivity based on such renewable energy sources as wind and the sun. Power contribution at the required proportion by the grids is the chief performance consideration which depends upon the penetration of distributed generation and the accessibility of conventional sources during the load transform. In this paper, the projected approach is that the essential load power is divided evenly between the grids composed of Distributed Generation (DG) units and the utility based on the PSO algorithm during the load transform. A case study is carried out based on the New England test system (10-Generator-39-Bus) as a standard by using Particle swarm optimization (PSO) algorithm.
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Kozak, Dariusz, Paweł Mazuro i Andrzej Teodorczyk. "Numerical Simulation of Two-Stage Variable Geometry Turbine". Energies 14, nr 17 (27.08.2021): 5349. http://dx.doi.org/10.3390/en14175349.
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The modern internal combustion engine (ICE) has to meet several requirements. It has to be reliable with the reduced emission of pollutant gasses and low maintenance requirements. What is more, it has to be efficient both at low-load and high-load operating conditions. For this purpose, a variable turbine geometry (VTG) turbocharger is used to provide proper engine acceleration of exhaust gases at low-load operating conditions. Such a solution is also efficient at high-load engine operating conditions. In this paper, the result of an unsteady, three-dimensional (3D) simulation of the variable two-stage turbine system is discussed. Three different VTG positions were considered for those simulations, along with three different turbine speeds. The turbine inlet was modeled as six equally placed exhaust pipes for each cylinder to eliminate the interference of pressure waves. The flow field at the outlet of the 1st stage nozzle vane and 2nd stage rotor was investigated. The simulations showed that the variable technologies significantly improve the efficiency of the two-stage turbine system. The highest overall efficiency of the two-stage system was achieved at 60,000 rpm and 11° VTG position.
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Chen, Xingbin, Xinhe Min, Peng Zhang, Nini Li, Zhihong Zhong i Yuansheng Wu. "Study on Impact Characteristics of Multistage Double Crown Face Gear Pairs considering Ratio Switching under Variable Conditions". Shock and Vibration 2020 (5.08.2020): 1–16. http://dx.doi.org/10.1155/2020/8880093.
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This paper presents a new transmission mechanism with multistage face gears as the core components for realizing variable speeds with differential meshing. To improve face gear transmission smoothness, suppress meshing resonance, reduce noise, and optimize power transmission performance during the gear shifting process, load distribution between meshing teeth during the transmission process and impact loads during various shifting stages must be determined. Herein, we present a gear impact model considering double crown gear meshing configuration, contact deformation, variable working conditions, and jump impact at meshing points. A single-stage face gear pair is considered as object that the impact characteristics are comparatively studied under four conditions: with/without load and constant/variable speed. The results were used to analyze transient characteristics of the crown gear under contact deformation or frequent shifting impact. Based on this, the impact characteristics of multistage face gear pairs between ratio switching were extendedly investigated under four input conditions: constant/variable torque or constant/variable speed. The results were used to determine the meshing force and impact force fluctuation characteristics of multistage face gear pairs while adapting to various loads and continuous acceleration/deceleration. The proposed model can be beneficial to evaluate the feasibility of multistage gear structures with crown configuration and to obtain boundary conditions for transmission systems.
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Zagar, Philipp, Helmut Kogler, Rudolf Scheidl i Bernd Winkler. "Hydraulic Switching Control Supplementing Speed Variable Hydraulic Drives". Actuators 9, nr 4 (4.12.2020): 129. http://dx.doi.org/10.3390/act9040129.
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Primary control of linear motion by variable speed electric motors driving a hydraulic cylinder via a constant displacement pump is an established and successful concept with a frequent use in industry. One problem arises when low or zero motion speed has to be realized under high pump pressure conditions. Such load scenarios occur frequently in certain pressing processes, e.g., for sintering or veneering. Most pumps have a lower speed limit, below which critical tribological conditions occur which impair lifespan and efficiency. In addition, pump speed control and pump fluctuation suffer from the mixed lubrication conditions in such an operation range. For a circumvention of such low speed pump operation, a digital valve control concept is presented and studied in this paper. Valve control is used in load holding phases with low speed. Pressure is provided by an accumulator which is charged by the pump in short charging cycles at reasonable pump speeds. It is shown that the mean control error during load holding phase lies within the desired band and the fluctuations of the control force are lower than those of the pump control. In addition, the unfavorable pump operation conditions can be avoided via digital control.
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Mroziński, Stanisław, Zbigniew Lis i Halina Egner. "Energy Dissipated in Fatigue and Creep Conditions". Materials 14, nr 16 (21.08.2021): 4724. http://dx.doi.org/10.3390/ma14164724.
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The paper presents the results of tests performed on samples made of P91 steel under combined variable and constant load conditions, at temperature T = 600 °C. The analysis of the test results was carried out with the use of the energetic description of the fatigue process. It was shown that the order of occurrence of the fatigue load and creep in the load program influences the fatigue life and the value of the energy cumulated in the sample until fracture.
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Argyropoulos, P., K. Scott i W. M. Taama. "Dynamic response of the direct methanol fuel cell under variable load conditions". Journal of Power Sources 87, nr 1-2 (kwiecień 2000): 153–61. http://dx.doi.org/10.1016/s0378-7753(99)00475-9.
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Moshrefzadeh, Ali. "Condition monitoring and intelligent diagnosis of rolling element bearings under constant/variable load and speed conditions". Mechanical Systems and Signal Processing 149 (luty 2021): 107153. http://dx.doi.org/10.1016/j.ymssp.2020.107153.
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Soroka, М. М. "LIMIT STATE OF ARCHES OF VARIABLE STIFFNESS". Bulletin of Odessa State Academy of Civil Engineering and Architecture, nr 81 (7.12.2020): 97–104. http://dx.doi.org/10.31650/2415-377x-2020-81-97-104.
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Abstract. An algorithm is proposed for numerically solving the problem of finding the maximum load for flat bar systems having a rectangular section of variable height. The material is elastoplastic; its physical properties are described by the Prandtl diagram. It is assumed that the compressive and tensile strength of the material are different. The modulus of elasticity in tension and compression is the same. The limiting state of a rectangular cross section under the simultaneous action of a longitudinal force and a bending moment is described. Using the proposed algorithm, a program was developed for calculating rod systems by the limit equilibrium. The C++ programming language was used to create a program for the numerical determination of the ultimate load for rod systems. The finite element method was used as the most universal to write a module that performs static analysis of the bar system. Its use makes it easy to design rod systems of arbitrary configuration with arbitrary boundary conditions. As a test example, a hinged circular arch loaded with a uniformly distributed vertical load is considered. Analytical dependences are written, which allow to obtain the ultimate load for an arch of variable section. Examples of calculating the limiting state of the arch and comparing the ultimate loads with and without longitudinal force are considered. The analytical solution is compared with the numerical solution found by the author's program. Good convergence of analytical and numerical solutions is shown. The proposed algorithm for the numerical calculation of the limit states uses the so-called direct method for finding the ultimate load. This allows not only to obtain the value of the ultimate load, but also to establish the order of formation of plastic regions in the sections of the rod system. The calculation algorithm does not imply the use of iterative processes, which has a positive effect on the speed of calculations. Within the accepted assumptions, the calculation methodology is accurate.
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Hu, Shengqiao, Houcai Liu, Huimin Kang, Puren Ouyang, Zhicheng Liu i Zhengjie Cui. "High Precision Hybrid Torque Control for 4-DOF Redundant Parallel Robots under Variable Load". Actuators 12, nr 6 (5.06.2023): 232. http://dx.doi.org/10.3390/act12060232.
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As regards the impact and chattering of 4-DOF redundant parallel robots that occur under high-speed variable load operating conditions, this study proposed a novel control algorithm based on torque feedforward and fuzzy computational torque feedback hybrid control, which considered both the joint friction torque and the disturbance torque caused by the variable load. First of all, a modified dynamic model under variable load was established as follows: converting terminal load change to terminal centroid coordinate change, then mapping to the calculation of terminal energy, and lastly, establishing a dynamic model for each branch chain under variable load based on the Lagrange equation. Subsequently, torque feedforward was used to compensate for the friction torque and the disturbance torque caused by the variable load. Feedforward torques include friction torque and nonlinear disturbance torque under variable load. The friction torque is obtained by parameter identification based on the Stribeck friction model, while the nonlinear disturbance torque is obtained by real-time calculation based on the modified dynamic model under variable load. Finally, dynamic control of the robot under variable load was realized in combination with the fuzzy computational torque feedback control. The experimental and simulation results show that the motion accuracy of the fuzzy calculation torque feedback and torque feedforward control of the three drive joints of the robot under variable loads is 49.87%, 70.48%, and 50.37% lower than that of the fuzzy calculation torque feedback. Compared with pure torque feedback control, the speed stability of the three driving joints under fuzzy calculation torque feedback and torque feedforward control is 23.35%, 17.66%, and 25.04% higher, respectively.
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Li, Qiang, Di Liu, Shen Chen, Zhu Liu, Wenjing Li, Lvchao Huang, Jinguo Fang i Yuqiang Zhuang. "Control strategy of bidirectional DC/DC converter under variable load state". Journal of Physics: Conference Series 2703, nr 1 (1.02.2024): 012087. http://dx.doi.org/10.1088/1742-6596/2703/1/012087.
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Abstract To improve the stability of DC/DC converters under multiple load conditions, the control strategy of Buck-Boost bidirectional DC/DC converters under variable load conditions is studied in this paper, as well as the droop control strategy for parallel operation of two machines. Based on the topology and basic control strategy of the DC/DC converter, a load current feedforward compensation strategy to achieve ideal stability of output voltage during load switching is studied; then charging and discharging control switching strategy under external power supply is proposed, which achieves fast switching between charging and discharging by sampling battery current and load voltage; finally, a current sharing control method based on inductance current droop is proposed for the parallel operation of two machines, achieving the control effect of equal current sharing between the two modules. The effectiveness and feasibility of the control strategy were verified through prototype experiments.
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Liu, Simin. "Study on Typical Aerodynamic Faults of Variable Pitch Wind Turbine". Frontiers in Computing and Intelligent Systems 3, nr 1 (17.03.2023): 16–20. http://dx.doi.org/10.54097/fcis.v3i1.6017.
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The variable-speed variable-pitch wind turbine is an important part of China's power and energy systems, and is also the main conversion form of wind energy utilization. Aiming at the problem that the traditional blade element-momentum theory cannot achieve the modeling and simulation of wind turbine plane wind unbalance caused by wind shear and tower shadow effect, the modeling and simulation numerical calculation method of aerodynamic load of wind turbine actuation disk with different blade wind unbalance pitch angles is proposed, This method can derive the analytical expressions for solving the key variables of load calculation, axial induction factor and tangential induction factor, and realize the aerodynamic load solution. At the same time, it is also verified that the characteristic vibration component of 3 times the low speed shaft rotation frequency (3P) is a typical dynamic load feature of tower shadow effect, and is also the most important aerodynamic load fluctuation feature of variable-speed variable-pitch wind turbine, However, under normal conditions, the wind shear effect has little effect on the wind turbine load fluctuation.
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Patel, Vimal. "Performance Investigation of Variable Compression Ratio Engine". International Journal for Research in Applied Science and Engineering Technology 9, nr 10 (31.10.2021): 1296–306. http://dx.doi.org/10.22214/ijraset.2021.38577.
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Abstract: Variable Compression Ratio (VCR) engine test can be used to determine the effect of Compression Ratio (CR) on the performance and emissions of the engine. The combustion situation, when provided with a pressure transducer. The performance frequency parameters like efficiencies, power, and specific fuel consumption are determined. The combustion phenomenon is also observed through this work, we can find the optimum compression ratio for which the best performance is possible. In order to find out the optimum compression ratio, experiments were carried out on a single-cylinder four-stroke variable compression ratio engine. Tests were carried out at compression ratios of 18, 17, and 16 at different loads the performance characteristics of the engine like Brake power (BP), Thermal Efficiency, Brake Specific Fuel Consumption (BSFC). A variable compression ratio engine is able to operate at different compression ratios, depending on particular vehicle performance needs. The VCR engine is optimized for the full range of driving conditions, as acceleration, speed, and load. Keywords: Performance, Compression ratio, Load, Break Power, William Line’s Method, Emission, Thermal Efficiency, Diesel Engine, Fuel Consumption
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Krishnamoorthy, Gautham, Evan Bloom, Krishnamoorthy Viswanathan, Shuchita Sanjay Patwardhan, David John Stadem i Steve Benson. "Measurements and Prediction of Ash Deposition in a Cyclone-Fired Boiler Operating under Variable Load Conditions". Fluids 8, nr 12 (23.11.2023): 305. http://dx.doi.org/10.3390/fluids8120305.
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Measurements of ash deposition rates were made between the secondary superheater and reheater sections of a 450 MW cyclone-fired lignite boiler as the operational load varied from 33 to 100%. Significant reductions in deposition rates with a decrease in operational load were observed. To uncover the causative mechanisms behind these observations, operational data from the power plant were used to carry out computational fluid dynamic (CFD) simulations of the boiler. After ascertaining that the gas temperatures and velocities at various sections within the boiler were being represented adequately, decoupled simulations of the ash deposition process on the deposit probe were carried out using a finely resolved boundary layer mesh. Fly ash particle size distribution (PSD) and its concentration for the decoupled calculations were determined from stand-alone cyclone barrel simulations. The ash partitioning (mass %) between the fly ash and slag was found to be ~50:50, which was in line with previous field observations, and it did not vary significantly across different cyclone loads. The predicted PSD of the deposit ash was concentrated in the size range 10–30 microns, which was in agreement with cross-sectional images of the deposit obtained from the measurements. At lower loads, sharp variations in the deposition rates were predicted in the gas temperature range 950–1150 K. The particle kinetic energy—particle viscosity-based capture methodology utilized in this study in conjunction with appropriate ash compositions, ash viscosity models and gas temperature estimates can help estimate slagging propensities at different loads reasonably well in these systems.
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Lee, Je-hyeon, Piljae Im, Jeffrey D. Munk, Mini Malhotra, Min-seok Kim i Young-hak Song. "Comparison Evaluations of VRF and RTU Systems Performance on Flexible Research Platform". Advances in Civil Engineering 2018 (2018): 1–16. http://dx.doi.org/10.1155/2018/7867128.
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The energy performance of a variable refrigerant flow (VRF) system was evaluated using an occupancy-emulated research building in the southeastern region of the United States. Full- and part-load performance of the VRF system in heating and cooling seasons was compared with a conventional rooftop unit (RTU) variable-air-volume system with electric resistance heating. During both the heating and cooling seasons, full- and part-load conditions (i.e., 100%, 75%, and 50% thermal loads) were maintained alternately for 2 to 3 days each, and the energy use, thermal conditions, and coefficient of performance (COP) for the RTU and VRF system were measured. During the cooling season, the VRF system had an average COP of 4.2, 3.9, and 3.7 compared with 3.1, 3.0, and 2.5 for the RTU system under 100%, 75%, and 50% load conditions and resulted in estimated energy savings of 30%, 37%, and 47%, respectively. During the heating season, the VRF system had an average COP ranging from 1.2 to 2.0, substantially higher than the COPs of the RTU system, and resulted in estimated energy savings of 51%, 47%, and 27% under the three load conditions, respectively.
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Dai, Peng, Jianping Wang, Shuping Yan, Shengzhou Huang, Fengtao Wang i Jun Liu. "Vibration characteristics of the gear shaft-bearing system with compound defects under variable operating conditions". Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics 236, nr 1 (6.12.2021): 113–29. http://dx.doi.org/10.1177/14644193211055021.
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Due to the variable working conditions, there are compound defects in the gear shaft-bearing system easily, vibration signals are very complex, and the fault diagnosis of the system becomes more difficult. Thus, a 36 degrees of freedom (36-DOFs) dynamic model is established for discussing the vibration characteristics of the gear shaft-bearing system, the gear pair spalling defect is considered, there are localized defects on the inner raceway and outer raceway of the supporting bearing, the work conditions contain variable speed, variable load, speed fluctuation, and load fluctuation. The obtained vibration signal is processed by the short-time Fourier transform for the time–frequency distribution map. When the gear shaft-bearing system with compound defects operates under variable conditions, roller passing outer raceway frequency, roller passing inner raceway frequency, gearing meshing frequency, and the relative harmonic frequencies can also be found. The defect frequencies and frequency amplitude are increasing with the speed while the system makes the accelerated movement. While the load acting on the system increases, the defect frequencies remain unchanged, but the frequency amplitude becomes larger. If there are fluctuations of the speed and load, the apparent defect frequency fluctuation and amplitude fluctuation is generated. The mathematical model and the analysis results are verified by the experiment, which will provide the theoretical basis for the fault diagnosis of the gear shaft-bearing system.
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Carreno, Alvaro, Marcelo Perez, Carlos Baier, Alex Huang, Sanjay Rajendran i Mariusz Malinowski. "Configurations, Power Topologies and Applications of Hybrid Distribution Transformers". Energies 14, nr 5 (24.02.2021): 1215. http://dx.doi.org/10.3390/en14051215.
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Distribution systems are under constant stress due to their highly variable operating conditions, which jeopardize distribution transformers and lines, degrading the end-user service. Due to transformer regulation, variable loads can generate voltage profiles out of the acceptable bands recommended by grid codes, affecting the quality of service. At the same time, nonlinear loads, such as diode bridge rectifiers without power factor correction systems, generate nonlinear currents that affect the distribution transformer operation, reducing its lifetime. Variable loads can be commonly found at domiciliary levels due to the random operation of home appliances, but recently also due to electric vehicle charging stations, where the distribution transformer can cyclically vary between no-load, rated and overrated load. Thus, the distribution transformer can not safely operate under highly-dynamic and stressful conditions, requiring the support of alternative systems. Among the existing solutions, hybrid transformers, which are composed of a conventional transformer and a power converter, are an interesting alternative to cope with several power quality problems. This article is a review of the available literature about hybrid distribution transformers.
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Karwowski, Waldemar, Bohdana Sherehiy, Paul Ray Gaddie, Tamer Khalaf i Peter M. Quesada. "The effects of lifting instructions on the psychophysically selected lifting load limits: A need for reappraisal". Occupational Ergonomics 7, nr 1 (14.06.2007): 43–51. http://dx.doi.org/10.3233/oer-2007-7105.
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This study investigated the effect of three different lifting instruction sets on the psychophysically selected loads. The instruction sets corresponded to three different load limit concepts: maximum acceptable weight of lift (MAWL), maximum comfortable weight of lift (MCWL), and maximum safe weight of lift (MSWL). Results demonstrated significant lifting instruction effects on the investigated dependent variables, including: selected load weight, selected load weight estimation, perceived physical effort, and perceived comfort and safety ratings associated with the selected load weights. Perceived acceptability of selected load weight was the only variable upon which lifting instructions did not have a significant effect. The results showed that the MAWL instruction led to selected loads that were significantly heavier than the loads selected under MSWL instructions. Also, the level of perceived physical effort under the MAWL condition was significantly higher than those obtained under the MSWL and MCWL conditions. Results from this study are consistent with previous research findings that psychophysical selection of lifting loads is very sensitive to the instructions provided to the subjects. It also is suggested that the application of the classical psychophysical approach to setting limits for manual materials handling tasks should be carefully reappraised.
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Subramani, Prabu, Sugadev Mani, Wen-Cheng Lai i Dineshkumar Ramamurthy. "Sustainable Energy Management and Control for Variable Load Conditions Using Improved Mayfly Optimization". Sustainability 14, nr 11 (25.05.2022): 6478. http://dx.doi.org/10.3390/su14116478.
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In recent trends, renewable energies are infinite, safe, and are becoming a reliable source for electricity requirements. However, they have certain variations in their results because of climate change, which is its major issue. To solve this challenge, a hybrid renewable energy system was created by combining various energy sources. Energy management strategies must be employed to determine the best possible performance of renewable energy-based hybrid systems, as well as to fulfil demand and improve system efficiency. This work describes an Energy Management System (EMS) for a Hybrid Renewable Energy System (HRES) called Improved Mayfly Optimization-based Modified Perturb and Observe (IMO-MP&O). The developed EMS is based on basic conceptual constraints and has the goal of meeting the energy demand of connected load, ensuring energy flow stabilization, and optimizing battery utilization. In addition, the suggested IMO-MP&O can identify the condition and operating state of every HRES sub-system and assure the network stability of frequency and voltage changes. Numerical simulations in the MATLAB/Simulink environment were used to evaluate the proposed EMS. The simulated results show that the proposed IMO-MP&O achieves the harmonic error of 0.77%, which is less than the existing Maximum Power Point Tracking (MPPT) control and Artificial Neural Network (ANN)-based Z-Source Converter methods.
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Burle, Trinadha, i V. V. S. Bhaskara Reddy Chintapalli. "Modified load flow algorithm suitable for modern power systems under variable weather conditions". Electric Power Systems Research 211 (październik 2022): 108221. http://dx.doi.org/10.1016/j.epsr.2022.108221.
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Umbrajkaar, A. M., A. Krishnamoorthy i R. B. Dhumale. "Vibration Analysis of Shaft Misalignment Using Machine Learning Approach under Variable Load Conditions". Shock and Vibration 2020 (30.07.2020): 1–12. http://dx.doi.org/10.1155/2020/1650270.
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The Industry 4.0 revolution is insisting strongly for use of machine learning-based processes and condition monitoring. In this paper, emphasis is given on machine learning-based approach for condition monitoring of shaft misalignment. This work highlights combined approach of artificial neural network and support vector machine for identification and measure of shaft misalignment. The measure of misalignment requires more features to be extracted under variable load conditions. Hence, primary objective is to measure misalignment with a minimum number of extracted features. This is achieved through normalization of vibration signal. An experimental setup is prepared to collect the required vibration signals. The normalized time domain nonstationary signals are given to discrete wavelet transform for features extraction. The extracted features such as detailed coefficient is considered for feature selection viz. Skewness, Kurtosis, Max, Min, Root mean square, and Entropy. The ReliefF algorithm is used to decide best feature on rank basis. The ratio of maximum energy to Shannon entropy is used in wavelet selection. The best feature is used to train machine learning algorithm. The rank-based feature selection has improved classification accuracy of support vector machine. The result obtained with the combined approach are discussed for different misalignment conditions.
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Facchi, A., C. Gandolfi i M. J. Whelan. "A comparison of river water quality sampling methodologies under highly variable load conditions". Chemosphere 66, nr 4 (styczeń 2007): 746–56. http://dx.doi.org/10.1016/j.chemosphere.2006.07.050.
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Teferra, Demsew Mitiku, Livingstone M. H. Ngoo i George N. Nyakoe. "Fuzzy-Swarm Intelligence-Based Short-Term Load Forecasting Model as a Solution to Power Quality Issues Existing in Microgrid System". Journal of Electrical and Computer Engineering 2022 (18.04.2022): 1–14. http://dx.doi.org/10.1155/2022/3107495.
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Load demand is highly stochastic and uncertain. This is because it was highly influenced by a number of variables like load type, weather conditions, time of day, the seasonality factor, economic constraints, and other randomness effects. The loads are categorized as holiday loads (national and religious), weekdays, and weekend days. The nonlinearity and uncertain characteristics of electrical load in a microgrid are one of the major sources of power quality problems in a microgrid system, and they can be handled using an accurate load forecast model. The fuzzy load prediction model can effectively handle these nonlinearity and uncertainty characteristics to have an accurate load forecast, but the main challenge with this model is its inability to accommodate a large volume of historical load and weather information when the membership function of the input and output fuzzy variables and the number of the fuzzy rules are tremendous. The swarm intelligence load forecast model based on particle swarm optimization algorithms can improve the limitations of the fuzzy system and increase its forecasting performance. The parameters of time, temperature, historical load, and error correction factors are considered as the Fuzzy and Fuzzy-PSO model input variables, while the forecasted industrial load is the only output variable. The Gaussian membership function is considered for both the input and output fuzzy variables. A 3-year historical hourly load data of an Ethiopian industrial system is used to train and validate both prediction models. The mean absolute percentage error (MAPE) is used to evaluate the performance of these prediction models. The Fuzzy-PSO load prediction model shows results that have superior performance to the fuzzy-alone load prediction results.
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Huang, Long, Yuemin Zhao, Yadong Zhang, Miao Pan, Haishen Jiang i Liang Dong. "Coupling mechanism of materials and screen surface motion in multi-stage variable inclination equal thickness screening process". Journal of Physics: Conference Series 2076, nr 1 (1.11.2021): 012087. http://dx.doi.org/10.1088/1742-6596/2076/1/012087.
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Abstract Multi-stage variable inclination equal-thickness screen (MSVIETS) is widely used in separating coal and mineral particles because of its large production capacity and good screening performance. In this study, the kinematic characteristics of infeed and outfeed ends surface under the conditions of load and no load was investigated by using a high-speed camera analysis system. The motion speed of the screen surface at the infeed end was approximately 5 times higher under load than under no-load conditions, and motion speed of the screen surface at the outfeed end was approximately 4 times higher than under no-load conditions. The mechanism of coupled motion of material and screen surface in the process of multi-stage variable inclination equal thickness screening was elucidated, and the energy coupling transfer law was “strong in and weak out”.
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Xie, Yingjiang, Fu Niu, Jinggong Sun i Lingshuai Meng. "Design and Analysis of a Novel Quasi-Zero Stiffness Isolator under Variable Loads". Mathematical Problems in Engineering 2022 (31.01.2022): 1–17. http://dx.doi.org/10.1155/2022/9082752.
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The designed load of most quasi-zero stiffness (QZS) isolators is constant. The isolation performance will drop sharply once the load changes. A novel QZS isolator that can adapt to variable loads is proposed in this paper to improve the range of application of the isolator. The isolator is designed by paralleling the electromagnetic spring (ES), which provides negative stiffness, and the pneumatic spring (PS), which provides positive stiffness. The positive and negative stiffness can be adjusted by changing the pressure and coil current, which provides the possibility for the isolator to adapt to variable loads. This paper derived the conditions for the isolation system to obtain QZS characteristics, proposed the dynamic model of the isolation system, derived and verified the analytical expressions of the amplitude-frequency response and force transmissibility (FT), and discussed the change of FT and displacement transmissibility(DT) under different loads. Theoretical analysis shows that changing the pressure and coil current in the same proportion can maintain the superior low-frequency isolation performance when the load changes, thanks to the preservation of the QZS characteristics of the system after adjusting the pressure and coil current. Finally, the simulation results fg and isolation frequency band over the linear isolation system and PS isolation system. Furthermore, the proposed isolator can be adjusted online.
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Chaudhari, Ashish J., Dnyaneshwar Panchal, Shankar Kolekar, Swapnil Kadav, Harshal Moradiya i Vinay D. Patel. "Performance Evaluation of Diesel Engine Using Novel Variable Compression Ratio Mechanism". Advanced Science, Engineering and Medicine 12, nr 11 (1.11.2020): 1417–21. http://dx.doi.org/10.1166/asem.2020.2608.
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Increasingly stringent emission and fuel economy standards brings opportunities and research in automobile engine technology development to make it more efficient and less polluting. There are various performance improvement strategies adopted by different researchers in order to get maximum power from the minimum quantity of fuel alongside substantial reduction in exhaust gas emission. The techniques such as CRDI (Common Rail Direct Injection), VVT (Variable valve timing) and such more are commercially viable and successfully incorporated in vehicles. Along the similar track, this paper highlights the importance of variable compression ratio diesel engine, method of achieving the variable compression ratio (VCR) as per load and speed conditions. Variable compression ratio (VCR) technology is one of the method for improving the automobile engine performance, efficiency, fuel economy with reduced emission for range of fuels. The basis of the VCR engine is to operate at different compression ratio, by altering the combustion chamber volume, as per need of most suitable operating conditions. Apart from this, the fuel injection location needs to be varied as per load and speed conditions. The synchronization of both VCR and variable fuel injector location (VFIL) becomes important. Knowing this fact, the study for the diesel Comet engine (3.7 kW@2100 RPM) is undertaken for variable clearance volume accompanied with VIPL. The work consists of design and development of mechanism consisting of auxiliary cylinder and auxiliary piston which will operate in and out of combustion chamber as per load and speed conditions. The detailed drawings and complete experimentation will be carried out to judge the improvement of performance of diesel engine with modification of variable clearance volume concept. The performance parameters consist of brake power, brake thermal efficiency and brake specific fuel consumption under various load conditions.
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Agyeman, Kofi Afrifa, Gyeonggak Kim, Hoonyeon Jo, Seunghyeon Park i Sekyung Han. "An Ensemble Stochastic Forecasting Framework for Variable Distributed Demand Loads". Energies 13, nr 10 (25.05.2020): 2658. http://dx.doi.org/10.3390/en13102658.
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Accurate forecasting of demand load is momentous for the efficient economic dispatch of generating units with enormous economic and reliability implications. However, with the high integration levels of grid-tie generations, the precariousness in demand load forecasts is unreliable. This paper proposes a data-driven stochastic ensemble model framework for short-term and long-term demand load forecasts. Our proposed framework reduces uncertainties in the load forecast by fusing homogenous models that capture the dynamics in load state characteristics and exploit model diversities for accurate prediction. The ensemble model caters for factors such as meteorological and exogenous variables that affect load prediction accuracy with adaptable, scalable algorithms that consider weather conditions, load features, and state characteristics of the load. We defined a heuristic trained combiner model and an error correction model to estimate the contributions and compensate for forecast errors of each prediction model, respectively. Acquired data from the Korean Electric Power Company (KEPCO), and building data from the Korea Research Institute, together with testbed datasets, were used to evaluate the developed framework. The results obtained prove the efficacy of the proposed model for demand load forecasting.
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Haro-Larrode, Marta. "Variable Reactance Criteria to Mitigate Voltage Deviations in Power Transformers in Light- and Over-Load Conditions". Machines 11, nr 8 (2.08.2023): 797. http://dx.doi.org/10.3390/machines11080797.
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In this paper, variable reactance (VR) criteria are proposed to mitigate voltage deviations in power transformers under light-load inductive and capacitive conditions, as well as for over-load conditions. Under capacitive load conditions, power transformers are affected by the Ferranti effect as much as AC lines are and can suffer damage if a large over-voltage is present at the secondary winding. A classical solution for this is the installation of expensive and bulky inductive reactors at different locations of the AC lines to absorb the reactive power. Instead, this paper addresses VR techniques focused on power transformer reactance modification to compensate for the over-voltage. With these techniques, the Ferranti effect on power lines can also be reduced. Another benefit is the cancellation of over-voltages whose cause is different from the Ferranti effect, namely under inductive load conditions. In addition, they can also enhance the parallel operation of power transformers by allowing more flexibility for overload sharing among transformers. The VR techniques are derived from the Kapp phasor-diagram theory and have been validated experimentally at a small scale in the laboratory. When implemented in a big network, they can also improve the load-flow voltage and AC line-loading profiles and even increase the power factor of certain generators.
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Khristich, Anna L., Svitlana A. Kolot i Viktor Polic. "Designing a professional burnout correction program based on life-purpose orientations in wartime conditions". Herald of Advanced Information Technology 6, nr 1 (10.04.2023): 81–96. http://dx.doi.org/10.15276/hait.06.2023.6.
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The work is devoted to substantiation of possibility of reduction of failure rate of thermal mode support system when operating with variable load by control of reliability indicators of thermoelectric cooler. A mathematical model for evaluating the effect of variable thermal load on reliability indicators of a single-cascade thermoelectric cooler at a given temperature level of cooling, medium temperature, geometry of thermocouple branches for various current modes of operation is considered. The relationship between the cooler steady-state operation time and mass and heat capacity of the structure, relative operating current and temperature difference is presented. The results of thermal load relation with operating current, refrigerating factor, time to steady-state mode, energy input, heat dissipation capacity of the radiator, and relative failure rate are presented. Calculations have been made at a given cooling temperature level, medium temperature, temperature differential, and thermocouple branch geometry for various characteristic current operating modes. It is shown that with decreasing thermal load at a given design of thermoelectric cooler, the value of operating current decreases, thus increasing the probability of no-failure operation. The obtained relationship of thermal load with operating current and relative failure rate serves as primary information for design of thermoelectric system for providing thermal modes of thermally loaded elements with variable thermal load. Using the rate of change of temperature difference between the thermally loaded element and the cold electrode of the cooler as a control feature, it is possible to reduce the failure rate when the thermal load decreases, which contributes to increasing the average probability of no-failure operation