Wormholes in the f(R,L,T) theory of gravity Moraes, P.H.R.S.; Agrawal, A.S.; Mishra, B.
Physics letters. B,
August 2024, 2024-08-00, 2024-08-01, Volume:
855
Journal Article
Peer reviewed
Open access
Morris and Thorne developed wormhole solutions in the late 1980s when they discovered a recipe that wormholes must follow for travelers to cross them safely. They describe exotic matter as satisfying ...−pr>ρ, where pr is the radial pressure and ρ is the energy density of the wormhole. This is a notable characteristic of the General Relativity Theory. The current article discusses traversable wormhole solutions in f(R,L,T)=R+αL+βT, with α and β are model parameters. The wormhole solutions presented here satisfy the metric constraints of traversability while remarkably avoiding the exotic matter condition, indicating that f(R,L,T) gravity wormholes can be filled with ordinary matter. The derived solutions for the shape function of the wormhole meet the required metric conditions. They exhibit behavior that is comparable to that of wormholes reported in earlier references, which is also the case for our solutions for the energy density of such objects.
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•Defining the RL fractional differences on hZ in the setting of Atangana Baleanu.•Defining the Caputo fractional differences on hZ in the setting of Atangana Baleanu.•Monotonicity ...analysis.•Fractional discrete mean value theorem.
In this article, benefiting from the nabla h−fractional functions and nabla h−Taylor polynomials, some properties of the nabla h−discrete version of Mittag-Leffler (h−ML) function are studied. The monotonicity of the nabla h−fractional difference operator with h−ML kernel (Atangana–Baleanu fractional differences) is discussed. As an application, the Mean Value Theorem (MVT) on hZ is proved.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The grounded inductance simulators using available commercially integrated circuit (IC) are proposed in this paper. The three types of active inductor called parallel R and L, series R and L and pure ...L are achieved. The proposed inductance simulators consist of single available commercially IC from Linear Technology Inc. called LT1228 with a resistor and a capacitor. The tune of inductance and resistance value can be done electronically. The proposed inductance simulators don’t require any active and passive component matching condition. The performances of proposed circuit are verified through PSPICE simulation and experiment. To show the usability of the proposed simulators, they are used to realize the sinusoidal oscillator, second order bandpass filter and second order band-reject filter. The workability of these applications is experimented. The results agree well with theoretical expect.
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•This paper proposes impedance protection configuration to enhance ride-through of DFIG based wind turbines during faults.•Impedance protection circuit configuration comprises of a parallel R-L ...impedance crowbar and a series R-L impedance circuit.•Proposed protection compensates deficiency of conventional protection schemes.•Improved performance of DFIG under transient-state is achieved with proposed protection scheme.
This paper proposes an impedance protection circuit configuration to enhance the ride-through of doubly-fed induction generators (DFIGs) based wind turbines (WTs) during faults. The proposed impedance protection circuit configuration comprises of a parallel R-L impedance crowbar and a series R-L impedance circuit. Traditionally, resistive-crowbar (i.e., R-crowbar) circuit is applied as the means of protection for the DFIG WT which efficiently protects the rotor-side converter (RSC) and dc-link capacitor against the effects of severe grid faults. However, the conventional R-crowbar circuit disconnects the RSC leading to the loss of generator excitation control. During that time, the WT generator becomes a conventional squirrel-cage induction generator (SCIG) which obtains its magnetization current from the point of common coupling (PCC) via stator winding terminals. This phenomenon further deepens the voltage-dip at the PCC. Alternatively, integrating the R-crowbar with series R-L branch partially maintains the RSC connection to the rotor winding. Hence the generator excitation control is also partially maintained but oscillations of the rotor currents and dc-link voltage can still affect the ride-through performances of WT driven by the DFIG. With the proposed protection circuit configuration, it compensates the deficiency of the two conventional protection circuits configuration. In order to validate the performance of the proposed scheme, extensive simulation studies are carried out using MATLAB/Simulink software. From the comparative simulation results, improved performances of the DFIG under transient-state are achieved with the proposed protection circuit configuration than the conventional protection circuits.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Summary
A new synthetic floating simulator topology is proposed which realizes lossy parallel inductance (R‐L), lossy parallel capacitance (R‐C), lossy parallel C‐D, and lossless floating capacitance ...multiplier (FCM) circuits using only three current feedback operational amplifiers (CFOA) as active elements and three impedances. In all the presented circuits, the value of L, C, and D is independently controllable through a single resistance without requiring any matching condition for passive elements. A novel feature of the proposed circuit involves a straightforward adjustment in the CFOA connections, allowing the circuit to function as either a floating lossless immittance simulator or a floating series‐type lossy immittance simulator. Various application examples of the presented circuits such as lead compensator, lag compensator, first‐order high‐pass filter, and fourth‐order Butterworth filter are also given to justify the theoretical analysis. To validate the workability of the proposed circuits, several analyses are conducted, including frequency analysis, transient analysis, Monte‐Carlo analysis, and temperature analysis, using the macro‐model of AD844 in the SPICE simulation tool. Experimental results of the parallel R‐L simulator and application examples are also provided using commercially available IC AD844‐type integrated CFOAs.
A new synthetic floating simulator topology is proposed which realizes lossy parallel inductance (R‐L), lossy parallel capacitance (R‐C), lossy parallel C‐D, and lossless floating capacitance multiplier (FCM) circuits using only three current feedback operational amplifiers (CFOA) as active elements and three impedances. In all the presented circuits, the value of L, C, and D is independently controllable through a single resistance without requiring any matching condition for passive elements. A novel feature of the proposed circuit involves a straightforward adjustment in the CFOA connections, allowing the circuit to function as either a floating lossless immittance simulator or a floating series‐type lossy immittance simulator. Various application examples of the presented circuits such as lead compensator, lag compensator, first‐order high‐pass filter, and fourth‐order Butterworth filter are also given to justify the theoretical analysis. To validate the workability of the proposed circuits, several analyses are conducted, including frequency analysis, transient analysis, Monte‐Carlo analysis, and temperature analysis, using the macro‐model of AD844 in the SPICE simulation tool. Experimental results of the parallel R‐L simulator and application examples are also provided using commercially available IC AD844‐type integrated CFOAs.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Summary
Incorporating the better impedance matching capability of planar curved radiating patch, a miniaturized broadband planar antenna has been designed, analyzed, and integrated with frequency ...selective surface (FSS) to accomplish higher gain for various short‐range and long‐range modern wireless communication applications. Physical and electrical volume of the presented antenna is 25 × 20 × 1.6
mm3 and 0.25
λ0 × 0.20
λ0 × 0.016
λ0, respectively. The proposed radiating patch is constructed from a conventional rectangular patch by transforming the upper side of the patch into a semi‐circular shape and the lower side of the patch into a staircase‐like shape. Measured outcomes of the designed antenna show a very large operating bandwidth of 19.8 GHz (3–22.8 GHz) with a fractional bandwidth (FBW) of 153.5% and bandwidth dimension ratio (BDR) of 3070. An equivalent circuit model (ECM) of the proposed antenna is developed using an advanced design system (ADS) circuit simulator. The frequency responses of the ECM are compared with the simulation done by CST Microwave Studio Suite software and measurement results, which show good agreement. An FSS structure with stop band from 2–28 GHz is positioned beneath the proposed antenna at optimal position (27 mm below the antenna) to enhance the gain up to 8.9 dBi. The presented antenna and FSS are fabricated on FR4 substrate and experimentally verified using standard microwave measurement setup.
Measured outcomes of the designed antenna show a very large operating bandwidth of 19.8 GHz (3–22.8 GHz) with a fractional bandwidth (FBW) of 153.5% and bandwidth dimension ratio (BDR) of 3070. An FSS structure with stop band from 2 to 28 GHz is positioned beneath the proposed antenna at optimal position to enhance the gain up to 8.9 dBi.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Abstract In the background of f ( R , L m ) gravity, this work investigates three distinct dark matter halo profiles to test the possibility of generalised wormhole geometry within the galactic halo ...regions. The current study aims to accomplish these goals by examining various dark matter profiles including universal rotation curves (URC), Navarro–Frenk–White (NFW) model-I, and NFW model-II inside two distinct f ( R , L m ) gravity models. According to the f ( R , L m ) = R 2 + L m α model, the dark matter (DM) halo density profiles produce suitable shape functions that meet all the necessary requirements for exhibiting the wormhole geometries with appropriate choice of free parameters. In addition, to examine DM profiles under the f ( R , L m ) = R 2 + ( 1 + λ R ) L m model, we consider a specific shape function. Further, we observed that the derived solution from both two models violates the null energy constraints, confirming that the DM supports wormholes to maintain in the galactic halo.
There has recently been a surge in demand for multi-hull vessels for military and commercial purposes. The need for multi-hull ships increase from the necessity to balance speed and cargo ...requirements. Among others, the trimaran is one such hull type. The current study performs a CFD resistance analysis for trimaran as a parameter range of feasible hull forms based on the NPL systematic series. The resistance of trimaran hull shapes are calculated using CFXTM, a commercial CFD code that belongs to ANSYS. The trimaran model was tested at one fixed transverse separation (S/L=0.2) together with 3 longitudinal separations, R/L=0, 0.25, and 0.5, at different Froude numbers (based on length) from 0.2 to 0.6. Testing on the individual hull is also carried out to quantify the effect of resistance interference on the trimaran configuration. The CFD simulation results indicate that the trimaran model with side hulls parallel to the stern (R/L=0) has the least resistance. The interference effect of resistance on Trimaran with R/L=0, 0.25, 0.5 are 2.8%, 4.6%, 6.8% as opposed to non-interference trimaran model, respectively. These findings provide an approach for appropriately selecting the trimaran model with longitudinal side hull configurations.
High-temperature superconducting (HTS) coils made of coated conductors that can operate in persistent current mode (PCM) are regarded to be promising in MRI/nuclear magnetic resonance and Maglev ...system. The temporal stability of the magnetic field trapped by the PCM coil is a key issue, which significantly determines the imaging quality of MRI and dynamic behavior of Maglev. This study focuses on the temporal stability of the trapped magnetic field in the double-slit HTS PCM coil, which is magnetized by a field cooling (FC) method at 77 K. The magnetic field decay behavior under different initial fields and FC ramp rates are systematically studied. The experiment results indicate that higher initially trapped field will lead to faster decay, but if the initially trapped field is lower than a certain value, this trend is no longer obvious. The FC ramp rate has a little impact on the field decay. Finally, a numerical model based on R-L circuit and E-J equation is established to fit the decay process. It is found that if the operating current is lower than 60% of the coil critical current, good temporal stability could be achieved. Another long-term experiment is performed that a stability of 8.1 ppm/h is achieved after 19 days' decay.
Non-commutativity is a key feature of spacetime geometry. The current article explores the traversable wormhole solutions in the framework of f(R,ℒm) gravity within non-commutative geometry. By using ...the Gaussian and Lorentzian distributions, we construct tideless wormholes for the nonlinear f(R,ℒm) model f(R,ℒm)=R2+ℒmα. For both cases, we derive shape functions and discuss the required different properties with satisfying behavior. For the required wormhole properties, we develop some new constraints. The influence of the involved model parameter on energy conditions is analyzed graphically which provides a discussion about the nature of exotic matter. Further, we check the physical behavior regarding the stability of wormhole solutions through the TOV equation. An interesting feature regarding the stability of the obtained solutions via the speed of sound parameters within the scope of average pressure is discussed. Finally, we conclude our results.
•The current article explores the traversable wormhole solutions in the framework of f(R,Lm) gravity within non-commutative geometry.•We used the Gaussian and Lorentzian distributions to construct tideless wormholes for the nonlinear model f(R,Lm)=R2+Lmα.•The ECs are analyzed graphically using the model parameter which provides a discussion about the nature of exotic matter.•We checked the physical behavior regarding the stability of wormhole solutions through the TOV equation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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