Maximum Operating Research Articles

Temperature Analysis of Single busbar With Variation of Total Harmonic Distortion in Current

Typically, busbars are used to transmit and distribute currents in a bus duct system. The alarming use of nonlinear loads in the industrial sector or at residentials, such as arc welding, computers, ballast lighting, variable speed drives, and so on, has resulted in the generation of harmonics in current distortion, which are uncontrolled and thus increase heat generation within the system. The research conducted in this paper focuses on the prediction of the heat distribution as well as the analysis on operating temperature of a single busbar with compliance to the British National and International Standard (BS 159: 2014) using the Finite Element Method (FEM) in COMSOL Multiphysics software. The copper busbar dimension used for this research was 20mm x 6mm x 300mm, and the fundamental Root Mean Square (RMS) current was 419.1 A. The size of this busbars can withstand the maximum current of 430 A at a maximum operating temperature of 90°C, which complies with the standard requirement. The fundamental current is injected with variation of total harmonic distortion in current up to 55% with an interval of 5%. According to the findings, the operating temperature increases in direct proportion to the increase in total harmonic distortion with the current injections. With the presence of 55% of total harmonics in the current, the current was increased up to 57.73 A from the fundamental current, while the operating temperature was increased up to 140C from the fundamental temperature. The total harmonics in current produced by the nonlinear loads could affect the operating temperature of the busbars, and this continuous operation of current flow will affect the busbars' lifespan due to the occurrence of overheating.

(L p,λ,μ,L q,λ,μ) boundedness of the G-fractional integral operator on G-Morrey spaces

Abstract In this paper we find conditions for the boundedness of the strong and weak fractional integral and fractional maximal operator generated by Gegenbauer differential operator on G-Morrey spaces.

Weighted Rellich and Hardy inequalities in L p(·) spaces

Abstract In this note we prove weighted Rellich–Sobolev and Hardy–Sobolev inequalities in variable exponent Lebesgue spaces L p ⁢ ( ⋅ ) ⁢ ( 𝔾 ) {L^{p(\,\cdot\,)}(\mathbb{G})} defined on stratified homogeneous groups 𝔾 {\mathbb{G}} . To derive the main results, we rely on weighted estimates for the Riesz potential operators in L p ⁢ ( ⋅ ) ⁢ ( 𝔾 ) {L^{p(\,\cdot\,)}(\mathbb{G})} , where 𝔾 {{\mathbb{G}}} is a general homogeneous group. The results are new even for the Abelian (Euclidean) case 𝔾 = ( ℝ d , + ) {\mathbb{G}=(\mathbb{R}^{d},+)} and the Heisenberg groups 𝔾 = ℍ n {\mathbb{G}={\mathbb{H}}^{n}} . The main statements are obtained for variable exponents satisfying the condition that the Hardy–Littlewood maximal operator is bounded in appropriate variable exponent Lebesgue spaces. We also give some quantitative estimates for the norms of integral operators involved in derived estimates.

A necessary condition for the boundedness of the maximal operator on $$L^{p(\cdot)}$$ over reverse doubling spaces of homogeneous type

AbstractLet $$(X,d,\mu)$$ ( X , d , μ ) be a space of homogeneous type and $$p(\cdot) \colon X \to[1,\infty]$$ p ( · ) : X → [ 1 , ∞ ] be a variable exponent. We show that if the measure $$\mu$$ μ is Borel-semiregular and reverse doubling, then the condition $${ess\,inf}_{x\in X}p(x)>1$$ e s s i n f x ∈ X p ( x ) > 1 is necessary for the boundedness of the Hardy–Littlewood maximal operator $$M$$ M on the variable Lebesgue space $$L^{p(\cdot)}(X,d,\mu)$$ L p ( · ) ( X , d , μ ) .

Maximal, Littlewood-Paley, Variation, and Oscillation Operators in the Rational Dunkl Setting

Maximal, Littlewood-Paley, Variation, and Oscillation Operators in the Rational Dunkl Setting

Benchmarking the Performance of Lithium and Sodium‐Ion Batteries With Different Electrode and Electrolyte Materials

ABSTRACTSodium‐ion (Na‐ion) batteries are considered a promising alternative to lithium‐ion (Li‐ion) batteries due to the abundant availability of sodium, which helps mitigate supply chain risks associated with Li‐ion batteries. Many studies have focused on the design of Li‐ion batteries, exploring their energy, power, and cost aspects. However, there is still a lack of similar research conducted on Na‐ion batteries. A comparison of the cell voltage characteristics and rate capability of sodium and lithium‐ion batteries using different types of electrodes and electrolytes. For sodium‐ion batteries electrolytes used are NaPF6 and NaClO4 and electrodes used are NaCoO2, NaNiO2, NaFePO4, (Na3V2(PO4)3), graphite, hard carbon, sodium metal, and sodium titanate. For lithium‐ion batteries with LiPF6 and KOH electrolytes and electrodes as LiCoO2, NMC, LVP, Li2MnSiO4, graphite, silicon, lithium titanate (LTO), lithium metal. A thorough analysis of six important performance metrics is part of the investigation: Ragone plots, Electrolyte salt concentration versus spatial coordinate, electrolyte potential versus spatial coordinate, Cell voltage versus battery cell state of charge, Cell voltage versus time, and state variable versus time. Comparing operating voltage and rated capacity NMC and graphite is selected for lithium‐ion batteries as this combination provides operating voltage up to 4.2 V and a rated capacity of 275 Wh/kg, for sodium‐ion for NaCoO2 and hard carbon which has an operating voltage of 2.5–3.8 V and rated capacity around 200 Wh/kg and another combination of electrode as NaFePO4 and sodium metal with NaClO4 electrolyte has a maximum operating voltage of 2.8–3.8 V and rated capacity around 200 Wh/kg. This paper shows significant influence of electrolyte selection on battery performance. The Ragone plots demonstrate that LiPF6 electrolytes in lithium‐ion batteries and NaPF6 electrolytes in sodium‐ion batteries both exhibit superior specific energy densities compared to their KOH and NaClO4 counterparts, respectively. The work presented in this paper encourages researchers to select alternate electrolytes and electrodes for lithium‐ion and sodium‐ion batteries in order to obtain optimal device performance.

Static and Dynamic Stress of the Combined Rotor with Curvic Couplings Considering the Rough Three-Dimensional Interface at Extreme Operating Conditions

The curvic coupling, as one of the common connecting structures for gas turbine combined rotors, is more susceptible to various dynamic and static loads at extreme operating conditions. But, traditional combined rotor models tend to neglect the influence of the connection structure, especially failing to consider the contribution of the curvic coupling interfaces. To address this problem, this paper establishes a solid geometric model of the combined rotor with curvic couplings considering the rough three-dimensional interfaces. The effectiveness of the proposed model method is indirectly verified through the compression tests and modal tests. Subsequently, combined with finite element calculations, the mechanical properties of the rotor with curvic couplings considering the rough interface are analyzed under static and dynamic load conditions. The results indicate that the roughness of the interface significantly affects the deformation of the contact surface under static load, but its impact on the overall deformation of the rotor is relatively insignificant. The dynamic stress at the interface exhibits periodic variations at the resonance speed. At the maximum operating speed, the dynamic stress is influenced by the magnitude of imbalance. The aforementioned methods and conclusions provide a reference for the design research and engineering application of combined rotors.

Enhancing microbial fuel cell performance with free-standing three-dimensional N-doped porous carbon anodes

Microbial fuel cells (MFCs) utilize microorganisms as catalysts to transform the chemical energy to electrical power. However, the practical application of MFCs is currently impeded by low power output, which is caused by insufficient microbial colonization on the anode, slow extracellular electron transfer at the microbe-anode interface, and low oxygen reduction reaction catalytic efficiency at the cathode. Herein, a three-dimensional (3D) hierarchical porous anode of Carbonization-CTS-MF/rGOtempreture (CCMF/rGOT) by pyrolyzing crosslinked composite of melamine formaldehyde resin (MF), chitosan (CTS) and graphene oxide (GO). The macroporous anode provides a biocompatible surface for exoelectrogens and 3D electron transfer pathways. In addition, an appropriate balance of graphitic-N and pyrrolic-N content optimizes both conductivity and the number of active sites, thereby synergistically enhancing extracellular electron transfer (EET) efficiency. Therefore, the power density of CCMF/rGO1000 anode is 11.28 W/m3, which surpasses the CCMF1000 anode without 3D reduced graphene oxide (rGO) conductive network (10.04 W/m3), and traditional carbon cloth anode (4.36 W/m3). Moreover, the anode runs stably for more than 200 days with a maximum operating voltage of 0.69 V, which achieves chemical oxygen demand (COD) removal rate of 95.4 %. This work provides a promising strategy to prepare a free-standing 3D anode with enriched exoelectrogens and enhanced EET to improve the MFCs performance.

Modelling and simulation of double-pantograph catenary system of Taiwan railway

Abstract In view of the insufficient transportation capacity of Taiwan Railways in populated urban areas and intercity railways, increasing the maximum operating speed can be a solution for the problem. However, it is unknown whether the overhead contact line (OCL) system of the Taiwan Railways can tolerate such speed changes. For the unique railway system used in Taiwan, the literature does not present research on the dynamic interaction behaviour for the typical EMU trains with two pantographs, which are widely used in Taiwan railway system. Further, in response to the government policy to localize the supply chain of railway components, this research aims to establish a reliable simulation model so that domestic manufacturers may use this model for the design and development of the pantograph-catenary system. In this study, the catenary system model is established based on theoretic principles, specifications and parameters are adapted from data used by Taiwan Railway Co. The pantograph model was constructed as multi-body model, with parameters taken from the pantograph equipped on the TEMU2000 tilting train. This model is used to analyse catenary system to investigate the potential loss of contact between the double pantographs and the contact wire with increased train speed. The loss of contact and other phenomena will be analysed to explore possible solutions or optimization strategies for catenary system design.

Sharp analytic version of Fefferman's inequality

Let T be a unit circle. Assume further that f is an element of the Hardy space H1(T) and g belongs to the analytic BMO space on T. The paper contains the identification of the optimal universal constant C in the estimate|12π∫Tf(ζ)‾g(ζ)dζ|≤C‖f‖H1(T)‖g‖BMO(T). Actually, the inequality is studied in the stronger form, involving the Littlewood-Paley function on the left and the sharp maximal function of g on the right. The proof rests on the construction of an appropriate plurisuperharmonic function on a parabolic domain and the application of probabilistic techniques.

The boundedness of the maximal operator in local “complementary” generalized Morrey spaces, associated with the Laplace-Bessel differential operator

We consider the generalized shift operator, associated with the Laplace-Bessel differential operator. The maximal operator, associated with the generalized shift operator are investigated. We prove that the B-maximal operator is bounded from the local ”complementary” generalized B-Morrey space

Variable Lebesgue Space over Weighted Homogeneous Tree

An infinite homogeneous tree is a special type of graph that has a completely symmetrical structure in all directions. For an infinite homogeneous tree T=(V,E) with the natural distance d defined on graphs and a weighted measure μ of exponential growth, the authors introduce the variable Lebesgue space Lp(·)(μ) over (V,d,μ) and investigate it under the global Hölder continuity condition for p(·). As an application, the strong and weak boundedness of the maximal operator relevant to admissible trapezoids on Lp(·)(μ) is obtained, and an unbounded example is presented.

On sharp heat kernel estimates in the context of Fourier–Dini expansions

We prove sharp estimates of the heat kernel associated with Fourier–Dini expansions on (0,1) equipped with Lebesgue measure and the Neumann condition imposed on the right endpoint. Then we give several applications of this result including sharp bounds for the corresponding Poisson and potential kernels, sharp mapping properties of the maximal heat semigroup and potential operators and boundary convergence of the Fourier–Dini semigroup.

Facile synthesis of mesoporous Co3O4 anchoring on the g-C3N4 nanosheets for high performance supercapacitor

The rational design of the hybrid supercapacitor is the proficient way to confront the problem addressed in the supercapacitor through the collective advantage of each material and even shows laudable electrochemical properties from intertwined effects. A hydrothermal technique was used to effectively incorporate cobalt oxide into layered g-C3N4 nanosheets for a high-performance-based hybrid supercapacitor. The nanocomposite of Co3O4/g-C3N4 (with 0.01 M Co3O4) achieved a maximum specific capacitance of approximately 455 F/g at a current density of 1 A/g. It exhibited 95 % cyclic stability over 10,000 cycles, without sacrificing its coulombic efficiency in a three-electrode configuration. The enhanced charge storage contribution arises from the effective incorporation of cobalt oxide into the layered carbon nitride, increasing the number of electrochemically active sites for electrolytic ions. A symmetric device was fabricated using a KOH gel-based electrolyte, delivering high energy and power density of 28.13 Wh/kg and 1.68 kW/kg, respectively, with a maximum cell operating voltage of 1.2 V. Furthermore, the device demonstrated excellent cyclic stability of 95 % with constant coulombic efficiency.

Hardy–Littlewood maximal operator in a new vanishing Orlicz–Morrey space

We study mapping properties of maximal operator in a new vanishing subspace of Orlicz–Morrey spaces. We show that the vanishing property defining that subspace is preserved under the action of maximal operator. As an application, we also investigate the behavior of fractional operators.

Bounds for Lacunary Bilinear Spherical and Triangle Maximal Functions

Bounds for Lacunary Bilinear Spherical and Triangle Maximal Functions

Mapping the techno-economic potential of next-generation CSP plants running on transcritical CO[formula omitted]-based power cycles

Although the thermodynamic potential of transcritical/supercritical power cycles running on CO2 mixtures for next generation Concentrated Solar Power plants has been already confirmed in literature, further investigation to assess the actual feasibility of this technology from a techno-economic standpoint is needed. In fact, large uncertainty is found when it comes to the estimation of the CapEx of the power block, and the same can be said for the solar subsystem when higher-than-SoA operating temperature are considered. In this paper, two CSP schemes, with different maximum operating temperatures, are studied: one employing molten salts and another based on solid particles.To overcome the high uncertainty in terms of cost estimation, a two-step analysis is developed: firstly, the CapEx of the entire plant, except for the power block, is calculated assuming correlations from literature. As a result, the minimum power block cost allowing an LCoE lower than a certain target is identified. Secondly, an inverse methodology is applied, setting the power block cost and assessing the minimum CapEx of the solar subsystem. As a result, a map is obtained showing the target CapEx to be accomplished by sCO2+CSP if a clear reduction of the LCoE of this technology is to be achieved.

Sobolev smoothing estimates for bilinear maximal operators with fractal dilation sets

Given a hypersurface S⊂R2d, we study the bilinear averaging operator that averages a pair of functions over S, as well as more general bilinear multipliers of limited decay and various maximal analogs. Of particular interest are bilinear maximal operators associated to a fractal dilation set E⊂[1,2]; in this case, the boundedness region of the maximal operator is associated to the geometry of the hypersurface and various notions of the dimension of the dilation set. In particular, we determine Sobolev smoothing estimates at the exponent L2×L2→L2 using Fourier-analytic methods, which allow us to deduce additional Lp improving bounds for the operators and sparse bounds and their weighted corollaries for the associated multi-scale maximal functions. We also extend the method to study analogues of these questions for the triangle averaging operator and biparameter averaging operators. In addition, some necessary conditions for boundedness of these operators are obtained.

Control of a 15MW off-shore wind turbine for black-start operation

Grid forming wind turbines are crucial for achieving a 100% renewable based grid. The mechanical control of the wind turbines is usually designed for maximum power tracking operation. This paper includes the development of a wind turbine pitch controller considering the wider operational range of a grid forming wind turbine. The proposed controller tracks the optimal generation characteristic of the wind turbine when grid connected and is designed to cater for the different power levels when the wind turbine is operated in islanded mode (or grid-connected at partial power). The proposed controller does not require wind speed estimation for its operation and shows better performance than standard pitch controllers during grid-forming operation, particularly, limiting wind turbine speed excursion during block de-loading. Moreover, the proposed controller does not increase the mechanical loads of the key wind turbine elements. The performance of the proposed control is validated in a black start procedure with a full wind farm realistic real-time simulator, including detailed electrical and aeroelastic models of the wind turbine generator, wind farm and connecting HVDC link. Time and frequency domain validation using the real-time model has shown the performance of the proposed controller during black start operation.

Hardy–Littlewood maximal function on Lorentz–Herz spaces

AbstractThis paper extends the study of the generalized Lorentz spaces to the Lorentz–Herz spaces. The Lorentz–Herz spaces consist of all Lebesgue measurable functions such that theirs non-increasing rearrangements belong to the weighted Herz space. The main result of this paper establishes the mapping properties of the Hardy–Littlewood maximal function on the Lorentz–Herz spaces.