Transient Analysis Technique Research Articles

Fundamental Investigation of the Transient Analysis Technique for Multilayered Dispersive Media by FILT Combined with Continued Fraction Expanded Method

Fundamental Investigation of the Transient Analysis Technique for Multilayered Dispersive Media by FILT Combined with Continued Fraction Expanded Method

A Novel Perspective on Enhancing Photocatalytic Performance through the Synergistic Effect of Nd Single Atoms and Heterostructures.

There are few reports on lanthanide single atom modified catalysts, as the role of the 4f levels in photocatalysis is difficult to explain clearly. Here, the synergistic effect of 4f levels of Nd and heterostructures is studied by combining steady-state, transient, and ultrafast spectral analysis techniques with DFT theoretical calculations based on the construction of Nd single atom modified black phosphorus/g-C3N4 (BP/CN) heterojunctions. As expected, the generation rates of CO and CH4 of the optimized heterostructure are 7.44 and 6.85 times higher than those of CN, and 8.43 and 9.65 times higher than those of BP, respectively. The Nd single atoms can not only cause surface reconstruction and regulate the active sites of BP, but also accelerate charge separation and transfer, further suppressing the recombination of electron-hole pairs. The electrons can transfer from g-C3N4:Nd to BP:Nd, with a transfer time of ≈11.4ps, while the radiation recombination time of electron-hole pairs of g-C3N4 is ≈26.13 µs, indicating that the construction of heterojunctions promotes charge transfer. The 2P1/2/2G9/2/4G7/2/2H11/2/4F7/2→4I9/2 emissions from Nd3+ can also be absorbed by heterostructures, which improves the utilization of light. The energy change of the key rate measurement step CO2 *→COOH* decreases through Nd single atom modification.

Dynamic Response of Thick Laminated Shells using Higher-Order Theory

In this paper, the dynamic characteristics of thick cross-ply laminated composite cylindrical shells are studied using a higher-order displacement model. The formulation accounts for the nonlinear variation of the in-plane and transverse displacements through the thickness, and abrupt discontinuity in the slope of the in- plane displacements at any interface. The effect of inplane and rotary inertia terms is included. The analysis is carried out using finite element approach. The governing equations derived using Lagrange's equations of motion are solved employing Newmark's direct integration technique for transient response analysis. The influences of various terms in the higher-order displacement field on the free vibrations, and transient dynamic response characteristics of cylindrical composite shells subjected to thermal and mechanical Loads are analysed.

A fractal effective permeability model for dual-wet porous Media

Recent studies have shown that the pores of some unconventional rocks can be categorized into hydrophilic pores that boarded by inorganic minerals such as quartz and hydrophobic pores that within the organic matter. The rock which consists of both hydrophilic and hydrophobic pores shows a dual-wettability behavior. The previously-proposed imbibition transient analysis technique has been applied in characterizing the pore size distribution of the dual-wet rocks by analyzing comparative oil and water imbibition data. On the basis of the determined pore size distribution, a fractal model for estimating effective permeability of the dual-wet rock was proposed. The proposed model, together with the imbibition transient analysis technique, is able to estimate effective permeability of the dual-wet rocks by using imbibition data. The proposed model can also estimate the effective permeability of hydrophilic pores and hydrophobic pores. The proposed model takes injection pressure, wettability behavior and pore size distribution of the dual-wet rock into the consideration. Our sensitivity analyses show that injection pressure affects effective permeability and hydrophobic permeability by controlling the water saturation within hydrophobic pores. The rock with higher volumetric fraction of hydrophilic pores tends to have higher hydrophilic permeability and lower hydrophobic permeability. By keeping the porosity constant, effective permeability decreases as the volumetric fraction of small pores increases. Cited as: Shi, Y., Guo, Y., Dehghanpour, H., Song, H. A fractal effective permeability model for dual-wet porous media. Advances in Geo-Energy Research, 2023, 8(2): 100-111. https://doi.org/10.46690/ager.2023.05.04

Transient Analysis on Excavator Bucket with Gray Cast Iron and Vanadium

Abstract: The excavator machines are power machines used in the Agricultural, Mining and Construction industry. The main purpose of this excavator is for digging, ground leveling and material transport operations etc. The excavator bucket part is subjected to various load forces. So in this project, the work is carried on the bucket by interchanging the composite materials like gray cast iron and vanadium. Since the bucket experienced so many loads like impact during digging transient analysis is carried out, the standard specimen prepared through stir casting technique and conducted tests on the specimen like tensile, compression, hardness, and impact test to validate the data. The main objective of this project is to design an excavator bucket using CATIA V5 software of 3-D modeling software. Then simulation did through ANSYS 19.2 software by transient analysis technique to know the deformation and stresses etc. And the results of deformation and stress are compared between Gray Cast Iron without Vanadium and Grey Cast Iron with Vanadium for comparing justified result.

Transient Stability Analysis and Enhancement Techniques of Renewable-Rich Power Grids

New techniques and approaches are constantly being introduced to analyze and enhance the transient stability of renewable energy-source-dominated power systems. This review article extensively discusses recent papers that have proposed novel and innovative techniques for analyzing and enhancing the renewable source-dominated power system’s transient stability. The inherent low-inertia characteristics of renewable energy sources combined with fast-acting power electronic devices pose new challenges in power systems. Different stability concerns exist for grid-following and subsequent grid-forming converter/inverter connections to power grids; hence, distinct solutions for enhancing the transient stability have been devised for each. Moreover, the fundamental concepts and characteristics of converter/inverter topologies are briefly discussed in this study. Recent discussions and reviews of analysis and enhancement techniques in transient stability could lead to new ways to solve problems in power systems that rely primarily on renewable energy sources.

Application of Transient Analysis Techniques to Fault Diagnosis in Low- and Medium-Power Synchronous Machines

Fault diagnosis techniques applied to synchronous motors such as Permanent Magnet Synchronous Machines (PMSMs) and Synchronous Reluctance Machines (SynRMs) are scarcely addressed in the literature, in strong contrast to the attention paid to asynchronous motors. In addition, the most widespread techniques are those based on steady-state condition analysis, and little attention is paid to detection during transient operation. The present paper aims to identify research gaps on the topic and to demonstrate the potential of transient analysis. First, the different diagnostic methodologies in literature are thoroughly analyzed. Then, two laboratory case studies are presented to demonstrate the potential of fault detection under non-stationary conditions for a PMSM and a SynRM. Stator current analysis is performed by building time–frequency maps to analyze the evolution of different fault indicators. The results show clear differences between healthy and faulty conditions during the transient regime.

Effect of heat treatments on metastable pitting of 316L stainless steel fabricated by selective laser melting

Effect of heat treatments on metastable pitting of 316L stainless steel fabricated by selective laser melting (SLM) was studied by scanning electron microscopy, potentiodynamic polarization, electrochemical noise (EN) and transient analysis techniques. The results show that the selective laser melted (SLMed) 316L stainless steel was composed of honeycomb cells with different orientations, and a small number of lack-of-fusion (LOF) pores were randomly distributed. After heat treatment, the honeycomb-like cellular structure transformed into austenite structure, and the non-metallic inclusions coarsened and grew. Non-metallic inclusions can be divided into two types according to the composition difference, one was manganese silicate enriched by Mn, Si and O and the other was MnS coexisted with the manganese silicate. The potentiodynamic polarization results show that the pitting potential of SLMed 316L stainless steel decreased after heat treatment. During the EN tests, three kinds of current transient were found, which corresponded to the metastable pitting initiated by the manganese silicate oxide inclusions, MnS coexisted with the manganese silicate and pore defects, respectively. Statistical analysis results of the transient signals show that the heat treatment reduced the nucleation rate of metastable pitting, and increased the transient amplitude, pit radius and pit stability product. The decreased pitting performance after heat treatment can be attributed to the low pit growth resistance.

A scanning pulse reaction technique for transient analysis of the methanol-to-hydrocarbons reaction

A method of scanning pulse gas chromatography (SP-GC) suitable for time-resolved analysis of transient response of catalysts to reactant pulses is introduced. Applied to the methanol-to-hydrocarbons reaction over several zeolite-based catalysts (HZSM-5, Ca/ZSM-5 and Ga/ZSM-5), SP-GC provided quantitative information about the transient reactivity and selectivity during methanol conversion. The SP-GC analysis demonstrates substantial differences in the relative rates of hydrocarbon formation between catalysts that favor aromatic or olefin cycles of the dual cycle hydrocarbon pool mechanism. The influence of metal promoters on the main reaction pathways was highlighted with an emphasis on mechanistic aspects.

Three-dimensional transient flow in heterogeneous reservoirs: Integral transform solution of a generalized point-source problem

Appraisal well testing plays a key role in optimizing a complex field’s exploitation strategy — and increasing complexity often calls for more elaborate reservoir models for the proper interpretation of each test’s results. The classical analytical methods usually require restrictive simplifying assumptions, which limit their usefulness when dealing with reservoir heterogeneity. We seek to solve this issue by applying the hybrid analytical–numerical Generalized Integral Transform Technique (GITT) to the pressure diffusivity equation — and specifically, to the point-source problem extended to a reservoir with arbitrary permeability variation irregularly distributed throughout the 3D domain. The technique is first demonstrated to produce an exact alternative form of the well-known solution to the classical point-source in a homogeneous reservoir. This equivalence is then used to derive a computationally efficient working expression for the generalized point-source in a heterogeneous reservoir. Finally, this building block is applied to construct a uniform flow solution for a limited entry vertical well through spatial superposition — thus demonstrating the usage of the GITT for other wellbore geometries. Synthetic examples are used to show that the obtained expressions are in good agreement with results from a commercial reservoir simulator. In all cases presented, the eigenfunction expansions for both the drawdown pressure and its logarithmic derivative converge to at least four and two significant digits, respectively, within the adopted practical ranges of the series’ truncation orders. It is clear that the pressure expansions have better convergence characteristics, which are also influenced by the time value and by the distance from the position under consideration to the point-source. The resulting novel solution to the point-source provided in the present work is the most general and least restrictive expression presented so far to this single problem in a heterogeneous domain, and it is suitable for pressure transient analysis. • Generalized Integral Transform Technique (GITT) for pressure transient analysis. • Generalization of the point-source solution for a heterogeneous reservoir. • Building block for any wellbore geometry — illustrated with the limited entry well.

Performance of the radial point interpolation method (RPIM) with implicit time integration scheme for transient wave propagation dynamics

The radial point interpolation method (RPIM) is combined with the appropriate implicit time integration technique for transient wave propagation analysis in this work. The dispersion error issue of the numerical results is investigated detailedly by performing the dispersion analysis. It is found that the RPIM with sufficiently large support domains of quadrature points is able to yield almost no spatial dispersion errors which are much lower than those from the traditional finite element (FE) approach with the identical node distributions, hence we can monotonically improve the computation accuracy of the numerical results by using the decreasing time steps, namely the present method shows the important and attractive monotonic convergence property for transient wave analysis. This property makes the present method clearly superior to the standard FE approach in transient wave analysis and much more accurate solutions can be achieved. Several typical benchmark problems of transient wave propagations are studied to assess the robust and superior performance of the present method over the conventional FE for transient wave analysis.

DIURNAL CIRCADIAN VARIATION IN PHOTOSYNTHESIS IN Dracaena sanderiana UNDER CONTRASTING TEMPERATURE AND LIGHT

Dracaena sanderiana is prominent and in-demand cut foliage in the global ornamental industry. This study was conducted to examine the stress responses of Dracaena sanderiana under contrasting temperature and light conditions by using chlorophyll fluorescence (ChlF) transient analysis technique. D. sanderiana cuttings were held in distilled water and subjected to two different light levels, i.e., 22,500±2,000 lux and 750±200 lux allowing two distinct temperature levels. The chlorophyll fluorescence data were collected through OJIP analysis using a portable fluorometer (FluorPen, FP 110). The measurements were recorded four times a day (9 am, 12 pm, 3 pm, and 6 pm) and the data were collected continuously for four days commencing from the first day of treatment application. The major parameters derived from the OJIP analysis, including specific energy fluxes per reaction center (ABS/RC, TR/RC, ET/RC, and DI/RC), flux ratios (maximum quantum yield of primary photochemistry-φPo, electron transport efficiency -ψo, and quantum yield of electron transport –φEo and maximum quantum yield of non-photochemical de-excitation- φDo), and performance index (PI) were recorded. ChlF data showed a clear unimodal diurnal variation in plant performances of D. sanderiana at 22,500±2,000 lux. The circadian variation was reported for all measured ChlF parameters except the ψo, TR/RC, and ET/RC. Based on these circadian variations of ChlF, it can be concluded that D. sanderiana displays a facultative CAM pathway as an adaptation to the stressed conditions.

On parameterized block symmetric positive definite preconditioners for a class of block three-by-three saddle point problems

In this paper, we consider some preconditioning techniques for a class of block three-by-three saddle point problems, which arise from a coupled diffuse element-finite element technique for transient coupled-field analysis and some other applications. Firstly, we propose an exact parameterized block symmetric positive definite preconditioner for solving the block three-by-three saddle point problems, and by analyzing the spectrum of the corresponding preconditioned matrix, we get that it has at most four distinct eigenvalues. Secondly, for the needs of practical applications, we also propose the inexact version of the above preconditioner for solving the block three-by-three saddle point problems, and through the analysis of the spectral properties of the corresponding preconditioned matrix, we obtain the bounds of its eigenvalues. In addition, we also study the choices of the (approximately) optimal parameters in the above inexact preconditioner. Finally, numerical experiments are performed to demonstrate the effectiveness of our proposed inexact preconditioner compared with the existing block preconditioners studied recently for the block three-by-three saddle point problems.

Extended Equal Area Criterion Revisited: A Direct Method for Fast Transient Stability Analysis

For transient stability analysis of a multi-machine power system, the Extended Equal Area Criterion (EEAC) method applies the classic Equal Area Criterion (EAC) concept to an approximate One Machine Infinite Bus (OMIB) equivalent of the system to find the critical clearing angle. The system-critical clearing time can then be obtained by numerical integration of OMIB equations. The EEAC method was proposed in the 1980s and 1990s as a substitute for time-domain simulation for Transmission System Operators (TSOs) to provide fast, transient stability analysis with the limited computational power available those days. To ensure the secure operation of the power system, TSOs have to identify and prevent potential critical scenarios through offline analyses of a few dangerous ones. These days, due to increased uncertainties in electrical power systems, the number of these critical scenarios is increasing, substantially, calling for fast, transient stability analysis techniques once more. Among them, the EEAC is a unique approach that provides not only valuable information, but also a graphical representation of system dynamics. This paper revisits the EEAC but from a modern, functional point of view. First, the definition of the OMIB model of a multi-machine power system is redrawn in its general form. To achieve fast, transient stability analysis, EEAC relies on approximate models of the true OMIB model. These approximations are clarified, and the EAC concept is redefined with a general definition for instability, and its conditions. Based on the defined conditions and definitions, functions are developed for each EEAC building block, which are later put out together to provide a full-resolution, functional scheme. This functional scheme not only covers the previous literature on the subject, but also allows to introduce several possible new EEAC approaches and provides a detailed description of their implementation procedure. A number of approaches are applied to the French EHV network, and the approximations are examined.

Maximizing the Benefit of Rate Transient Analysis for Gas Condensate Reservoirs

In recent years, many trials have been made to use the Rate Transient Analysis (RTA) techniques as a method to describe the gas condensate reservoirs. The problem with using these techniques is the multi-phase behavior of the gas condensate reservoirs. Therefore, the Pressure Transient Analysis (PTA) is commonly used in this case to analyze the reservoir parameters. In this paper, we are going to compare the results of both PTA and RTA of three wells in gas condensate reservoirs. The comparison showed a great match between the results of the two mentioned techniques for the first time using a reference GOR of 75,000 SCF/STB. Therefore, we concluded that we could depend on RTA instead of PTA to spare the cost associated with the PTA in the gas condensate reservoirs.

Statistical correlation technique for transient signal analysis during impulse testing of transformers

The reliable technique for identification of winding insulation faults in a transformer is necessary for a testing engineer during impulse test. In this study, a statistical correlation technique is proposed to estimate the ‘best correlation’ between transient signals for passed (withstood the impulse voltage) or failed (not withstood) conditions of the insulations. In this study, normalised reduced impulse voltage is considered initially as a reference signal. The next successive impulse test sequences due to rated test voltage are correlated as a test signal with a reference signal using a proposed technique. It makes a ‘good correlation value along with its directions’ between the reference signal and test signal based on measured the applied impulse voltage waveshape and its winding response. The fundamentals of the correlation coefficient, curve fitting techniques, conditional variance, normalisation and time delay index are integrated effectively to predict the characteristics (degree/magnitude and direction) of correlation between the signals. 2.5-MVA 11/0.433 kV (distribution transformer), 0.3-MVA 34.5/0.415 kV (earthing transformer) and 250-MVA 500/275/33 kV (power transformer) are effectively utilised to validate proposed technique. The advantage of the proposed technique is validated with partial discharge detection in windings due to an impulse voltage application using an 11 kV single-layer winding.

Rate transient analysis of infinite-acting linear flow by use of piecewise constant diffusivity coefficients

Rate transient analysis (RTA) techniques are developed based on the analytical solutions to the hydraulic diffusivity equation. The diffusivity equation is subject to nonlinearity caused by the dependency of the rock and fluid properties to pressure. In this study, first, we develop a semi-analytical model to solve a nonlinear diffusivity equation for transient linear flow under the constant bottom-hole pressure condition. We use piecewise constant diffusivity coefficients to linearize the diffusivity equation. The domain under consideration is divided into an arbitrary number of subdomains. Each subdomain is assigned with a constant hydraulic diffusivity coefficient. As a result, the nonlinear diffusivity equation is reduced into a set of piecewise linear equations. Further, we propose a new RTA approach using the developed semi-analytical model. We then validate both the semi-analytical model and the RTA approach against direct numerical simulation. The comparison reveals the high accuracy of the developed model in the estimation of reservoir properties, pressure profiles, and flow rates, including the cases with highly pressure-dependent properties. Finally, we apply the proposed RTA approach to the flowback and long-term production data obtained from two horizontal wells to determine the reservoir properties, such as the cross-sectional area to flow and initial permeability. The field applications demonstrate that the proposed RTA approach provides a rigorous avenue for production data analysis of pressure-sensitive formations during transient linear flow.

Locating ground faults in non-solidly grounded networks via nonlinear least-squares

This paper presents a method for locating ground faults in ungrounded and high resistance grounded networks. In such networks, the contribution of the fault to the line currents is minimal, thus creating a challenge to the popular impedance-based fault locators employed in the industry. A compensation method is introduced to alleviate this impediment to the use of impedance-based fault locators; the compensated signals are consistent with the transmission line wave equations and are formed by the fault signal components thus making the fault information more visible. The proposed approach employs (i) phasor extraction based on forward and backward finite impulse response (FIR) filtering to better capture the fault signal dynamics, (ii) an initialization stage employing redundant measurement equations of the fault voltage, and (iii) an augmented matrix approach for least-squares estimation that models the physical conditions of the fault in symmetrical component coordinates. The proposed method is contrasted with a recent transient analysis technique for locating ground faults in non-solidly grounded systems and a synchronized measurement technology-based fault locator; the numerical results show a significant improvement in accuracy while employing standard data acquisition devices.

Transient analysis of finite multi‐conductor transmission line metamaterials (MTL‐MMs) based on discrete green's function (DGF) and macro‐modelling techniques

A new systematic macro-modelling technique for transient analysis of finite multi-conductor transmission line metamaterials (MTL-MMs) based on a Dyadic discrete Green's function (DGF) approach is proposed. Governing discrete voltage-based equations for one- and two-dimensional (1-D and 2-D) MTL-MMs are derived using a rigorous MTL analysis. Applying the idea of the Dyadic DGF solution to these equations, the impedance matrix representation of a finite open-ended MTL-MM is represented in a rational form, where the corresponding poles and residues can be identified exactly. The resulting pole/residue macro-model is converted into a state space model which is compatible to SPICE circuit simulator. The proposed macro-modelling technique significantly reduces the CPU time for transient analysis of 2-D electromagnetic band gap (EBG) structures embedded in large multi-layer printed circuit boards or volumetric NRI slabs with interaction with free space waves which can be modelled as an MTL-MM system. The usefulness of the proposed macro-model is illustrated by three sample MTL-MMs including 1-D shunt node negative refractive index ( NRI ) slab and 2-D two- and three-layered shielded EBG structures. The obtained results from the proposed macro-modelling technique are presented and compared with those obtained using a full-wave simulator, confirming the validity of the proposed model.

Application of the Method of Analysis of Periodic Modes for the Calculation of Transients in Electronic Circuits

Transient analysis is one of the most computationally intensive types of electronic circuits’ analysis. Typically, circuit simulators perform a numerical integration of the mathematical model of a circuit, which consists of a set of differential and algebraic equations, in order to find the transient response of a circuit. The maximum achievable accuracy of the transient solution is limited to the accuracy of the numerical integration method. The integration is performed point-by-point, so the error of the solution is accumulated. This is not the issue for most of the methods of periodic steady-state analysis, however these methods are not suited for the transient analysis.In our paper we develop a transient analysis technique with usage of the discrete singular convolution method, that is intended for periodic steady-state analysis. Discrete singular convolution method decomposes unknown signals in a circuit into Shannon’s series, and the derivatives of these signals are represented by the derivatives of the series. In this way, the mathematical model of a circuit is transformed into a set of nonlinear algebraic equations, which can be solved using, for example, Newton-Raphson method. The expression for the derivatives approximation can be presented in a matrix form, which leads to simple matrix equations in the mathematical model of the circuit. The derivatives matrix is independent of the unknown signals in the circuit, and it is defined only by the derivative of the Shannon kernel. The coefficients of this matrix do not change through the iterative process for a fixed number of samples. The matrix should be calculated only once, before starting the Newton-Raphson iterative procedure. It should be recalculated only if the number of samples was changed in order to improve accuracy.In order to apply the discrete singular convolution to the transient analysis problem, an arbitrary aperiodic waveform of the input source is repeated with the period that exceeds the duration of the transient processes in a circuit. In this way, the transient solution is found simultaneously in all time points, so the error is not accumulated as if the solution is calculated point-by-point. As an example of an arbitrary waveform, the Heaviside step function can be used.As far as the discrete singular convolution method is suitable for nonlinear circuits, the proposed technique is suitable for transient analysis of nonlinear circuits either.Three examples are given to illustrate the application of the new technique.Ref. 15, fig. 10.