Conventional Energy Method Research Articles

Balancing growth and sustainability: The impact of Greenfield investment on trade adjusted carbon emissions

In the last two decades, the surge in carbon emissions has escalated environmental damage and is a major concern globally. Recognized as a significant threat to humanity, unchecked environmental degradation can potentially hinder the achievement of sustainable development. As a result, accurate monitoring of carbon emissions becomes imperative for formulating effective climate policies. Taking into consideration, this study has taken the newly developed consumption-based carbon emissions measure to study the pollution haven hypothesis and examine the link between Greenfield Investment (GFI) inflows to host nations and their environmental impact for 85 developing countries from 1990 to 2020. The results show a positive correlation between Greenfield investment and Consumption-based Carbon Dioxide Emissions (CCO2) in sampled nations. Similarly, energy usage and export damage the environment because developing countries rely on conventional and old methods of energy usage. The results were further analyzed for low, lower middle, and upper middle income countries as well. The subsample outcome shows that Greenfield investment has a more damaged environment in low income countries as compared to lower middle and upper middle income countries. These insights underscore the urgency for developing countries to adopt environmentally conscious policies to attract international investors. It also emphasizes the need for stringent regulations aimed at curbing environmental pollution and complying with the Sustainable Development Goals (SDGs). Similarly, low and lower middle income countries to attract Greenfield investment, may also focus more on strict environmental pollution policies. Industries must be shifted from conventional energy methods to renewable energy sources. Sustainable Development Goals; 7, 12, and 13 can be achieved by host countries, alluring investors to invest in terms of Greenfield in renewable energy resources, which would be used in automobile transportation, to shift industries from conventional energy resources to renewable energy resources. The same Greenfield investment would also be used in bringing efficient machinery for more production in industries with minimal environmental pollution.

Elastic Lateral Torsional Buckling of Beams Under External Moments: A New Type of Nonconservative Problem

The important character of the applied moment with a fixed line of direction as implied in deriving the governing differential equations of LTB for elastic beams, however, is not represented in stating the boundary conditions based on conventional energy approaches. This paper sets out to consider the boundary conditions derived by conventional potentials in order to identify the ignored second-order moments that need to be added for maintaining the initial direction of the applied moment during LTB. By taking into account the non-zero work done by these ignored moments for modifying original potentials, the nonconservative nature of the elastic LTB of beam under external moments is clarified in two aspects — by discovering the path-dependent property of the non-zero work and by demonstrating that only trivial solution of LTB mode is expected from the analytical solution of the governing differential equations. Using the concept of dynamic instability, an analysis procedure combining the numerical solution of an eigen-value problem and the bisection method is proposed to identify the first appearance of imaginary or conjugate complex frequencies and to determine the value of the critical moment. Demonstrative examples are considered for illuminating the elastic LTB behavior using conventional energy methods and revised virtual work equation. It has been found that the critical moments given by conventional potentials are generally not consistent with each other unless the work done by the ignored second-order moments vanishes. However, consistent critical moment, under which the free vibrating amplitude of elastic beam is increased unboundedly with time, can be obtained by the kinetic approach based on any revised virtual work equation, indicating the necessity of considering the nonconservative nature of non-follower applied moment.

Comparison of Two Analytical Methods for Calculating Cogging Torque Based on Homopolar Inductor Machines

Cogging torque can cause the torque ripple and noise of machines and reduce the machine control accuracy. The analytical calculation method of cogging torque has always been a hot research topic in the field of machine. Conventional energy method is usually adopted to compute the cogging torque. Recently, a novel energy method is proposed. To reveal the fundamental difference and respective merits of these two energy methods, this paper first derives the analytical models of cogging torque in homopolar inductor machines (HIMs) considering the leakage fluxes of the stator slots by the two energy methods. Based on the derived analytical models, the cogging torque production mechanisms expressed by the two energy methods are analyzed and compared from the viewpoint of air-gap field modulation principle. The cogging torque computed by the two energy methods is all produced by the interactions of the air-gap magnetic fields modulated by the harmonics of the air-gap magnetomotive force (MMF) and air-gap permeance. However, due to the difference in the approaches of solving the air-gap magnetic field energy density, the novel energy method takes into account more harmonics of the air-gap MMF and air-gap permeance. Furthermore, the computational accuracy and complexity of the two energy methods are analyzed and compared based on the analytical calculations and three-dimensional (3-D) finite element analysis (FEA) for the cogging torque in a 48-slot/4-pole (48S4P) permanent magnet (PM) HIM and a 45-slot/6-pole (45S6P) field winding HIM. Compared with the conventional energy method, the novel energy method has higher accuracy, but is more complex. Finally, a prototype of the 48S4P PM HIM is manufactured. The results of analytical calculation, 3-D FEA and comparison are verified by experiments.

A New Reconstruction Algorithm for Geometric Shape of Static Overhead Transmission Lines

This paper proposes a reconstruction algorithm for the geometric shapes of static overhead transmission lines that is based on the spatial coordinate data (obtained by field mapping) and the corresponding inclination data (obtained by attitude sensors). The algorithm takes the piecewise cubic Hermite interpolation function as the basic framework and corrects the aforementioned two types of data based on the “minimum energy principle” of the transmission line system. The introduction of a new energy function in modified energy method (MEM) overcame the shortcomings of conventional energy method (CEM) in fairing strategy, and the new Fairing Criterion made result curves more consistent with the mechanical properties of transmission lines. In the numerical simulation tests, the two energy methods were compared in terms of load type, horizontal span, elevation difference, and anti-disturbance ability, which showed that MEM has a higher reconstruction accuracy (average Euclidean distance is less than 1 cm) and better robustness than CEM. Meanwhile, the key parameters involved in the algorithm were discussed to guide the application in practical engineering. In addition, measurement tests under non-uniform icing were carried out in the field test station, and the results showed that the maximum relative error is less than 0.1%.

A spatial–temporal analysis approach for flutter predictions using decoupled and fully-coupled methods

Accurate and efficient numerical predictions of flutter is essential for the turbomachinery industry. The decoupled method has been the main workhorse of the industry for decades thanks to its low computational resources required. However, there arises the need for an innovative propulsion architecture and a lightweight material, which hinders the accuracy and effectiveness of the decoupled method. Hence, the use of fully-coupled methods for flutter predictions has been steadily increasing. Despite more demanding computational resources needed to perform the fully-coupled simulations, the large amount of data generated in the time-domain is not often used efficiently. Typically the aeroelastic stability is judged in a straightforward manner using the logarithmic decrement. Although this global parameter is useful to compare the aeroelastic stability among configurations, it yields almost no meaningful understanding of the physical vibration mechanisms. In the present paper, a spatial–temporal analysis approach based on the Hilbert transform is proposed. It can work well with the non-linear non-stationary data typically generated from the time-domain fully-coupled solutions. In addition, the Hilbert transform-based analysis approach is designed to be consistent with the conventional energy method when the newly developed method is applied to the decoupled simulation data. The Hilbert transform-based approach is applied to three computational examples, each with a particular aeroelastic flow mechanisms of interest (i.e. tip clearance, laminar separation bubble, stall). The new approach has been shown to effectively elucidate the associated vibration mechanisms using the decomposition method in space and time.

Comparison methods for a Keller–Segel-type model of pattern formations with density-suppressed motilities

This paper is concerned with global existence of classical solutions as well as occurrence of infinite-time blowups to the following fully parabolic system 1 $$\begin{aligned} {\left\{ \begin{array}{ll} u_t=\varDelta (\gamma (v)u)\\ v_t-\varDelta v+v=u \end{array}\right. } \end{aligned}$$ in a smooth bounded domain $$\varOmega \subset {\mathbb {R}}^n$$ , $$n\ge 1$$ with no-flux boundary conditions. This model was recently proposed in Fu et al. (Phys Rev Lett 108:198102, 2012) and Liu et al. (Science 334:238, 2011) to describe the process of stripe pattern formations via the so-called self-trapping mechanism. The system features a signal-dependent motility function $$\gamma (\cdot )$$ , which is decreasing in v and will vanish as v tends to infinity. An essential difficulty in analysis comes from the possible degeneracy as $$v\nearrow \infty .$$ In this work we develop a novel comparison method to tackle the degeneracy issue, which greatly differs from the conventional energy method in literature. An explicit point-wise upper-bound estimate for v is obtained for the first time, which shows that v(x, t) grows point-wisely at most exponentially in time. An intrinsic mechanism is then unveiled that the finite-time degeneracy is prohibited in any spatial dimension with a generic decreasing $$\gamma $$ . With such new findings, we further study global existence of classical solutions when $$n\le 3$$ and discuss uniform-in-time boundedness when $$\gamma (\cdot )$$ decreases algebraically at large signal concentrations. Besides, a new critical-mass phenomenon in dimension two is observed if $$\gamma (v)=e^{-v}$$ . Indeed, we prove that the classical solution always exists globally and remains uniformly-in-time bounded in the sub-critical case, while in the super-critical case a blowup may take place in infinite time rather than finite time.

Analysis of Friction-Saturated Flutter Vibrations With a Fully Coupled Frequency Domain Method

Abstract Flutter stability is a dominant design constraint of modern turbines. Thus, flutter-tolerant designs are currently explored, where the resulting vibrations remain within acceptable bounds. In particular, friction damping has the potential to yield limit cycle oscillations (LCOs) in the presence of a flutter instability. To predict such LCOs, it is the current practice to model the aerodynamic forces in terms of aerodynamic influence coefficients for a linearized structural model with fixed oscillation frequency. This approach neglects that both the nonlinear contact interactions and the aerodynamic stiffness cause a change in the deflection shape and the frequency of the LCO. This, in turn, may have a substantial effect on the aerodynamic damping. The goal of this paper is to assess the importance of these neglected interactions. To this end, a state-of-the-art aero-elastic model of a low pressure turbine blade row is considered, undergoing nonlinear frictional contact interactions in the tip shroud interfaces. The LCOs are computed with a fully coupled harmonic balance method, which iteratively computes the Fourier coefficients of structural deformation and conservative flow variables, as well as the a priori unknown frequency. The coupled algorithm was found to provide excellent computational robustness and efficiency. Moreover, a refinement of the conventional energy method is developed and assessed, which accounts for both the nonlinear contact boundary conditions and the linearized aerodynamic influence. It is found that the conventional energy method may not predict a limit cycle oscillation at all while the novel approach presented here can.

An overview of global renewable energy trends and current practices in Pakistan—A perspective of policy implications

Sustainable, efficient, and affordable energy supply embraces a strong relationship with socio-economic development, specifically in developing countries. Pakistan has been facing an energy crisis in the form of expensive electricity generation by largely depending upon fossil fuels and experiencing power shortages. This paper offers a thorough analysis of Pakistan's renewable energy (hereinafter RE) potential and current practices, in trying to meet its energy demands. There is a limited academic discussion available concerning the utilization of RE resources of Pakistan to produce cost-effective and cost-competitive energy, including the formulation of pertinent laws and policies. This study adopts qualitative means to investigate global trends and current practices in renewables, followed by concrete observations and recommendations to improve the situation in Pakistan. The objective of the study is, therefore, to establish the significance of renewables and to examine possible solutions available to the government of Pakistan in addressing its energy crisis. The study concludes by suggesting that there is an urgent need to follow the global trend in replacing conventional energy methods with the country's extensive RE resources in order to ensure sustainable economic security and growth.

Distortional buckling calculation method of steel-concrete composite box beam in negative moment area

'Distortional buckling' is one of the predominant buckling types that may occur in a steel-concrete composite box beam (SCCBB) under a negative moment. The key factors, which affect the buckling modes, are the torsional and lateral restraints of the bottom plate of a SCCBB. Therefore, this article investigates the equivalent lateral and torsional restraint rigidity of the bottom plate of a SCCBB under a negative moment; the results of which show a linear coupling relationship between the applied forces and the lateral and/or torsional restraint stiffness, which are not depended on the cross-sectional properties of a SCCBB completely. The mathematical formulas for calculating the lateral and torsional restraint rigidity of the bottom plate can be used to estimate: (1) the critical distortional buckling stress of SCCBBs under a negative moment; and (2) the critical distortional moment of SCCBBs. This article develops an improved calculation method for SCCBBs on an elastic foundation, which takes into account the coupling effect between the applied forces and the lateral and/or torsional restraint rigidity of the bottom plate. This article analyzes the accuracy of the following calculation methods by using 24 examples of SCCBBs: (1) the conventional energy method; (2) the improved calculation method, as it has been derived in this article; and (3) the ANSYS finite element method. The results verify that the improved calculation method, as it has been proved in this article, is more accurate and reliable than that of the current energy method, which has been noted in the references.

Study on Malaysian's Perspective Towards Renewable Energy Mainly on Solar Energy

Malaysia, despite being known as the suppliers for oil and natural gas in the world is having a hard time fulfilling the huge demand of domestic and international energy sector. The nation's oil production has been gradually decrementing since reaching a peak of 862,000bbl/d in 2004 due to mature reservoirs. Alternative Cost as well as the maintenance that remains increasing yearly while the supply of fuels are depleting is making it hard for Malaysia to be able to sustain its oil development. This has become an important issue for the government to establish energy in the most economically worthy to ensure the sustainability in its development. This paper presents a review on Malaysian's perspective on renewable energy mainly in the solar energy sector by conducting a survey study. The survey focuses on the level of understanding Malaysian has towards renewable energy, the level of acceptance towards solar energy, the future prospect of solar energy as well as the financial perspective on solar energy in Malaysia. Study shows that renewable energy mainly in the area of solar energy receives warm welcome from many Malaysian as well as a demand for change in the conventional energy method. Malaysian is also ecologically concern as well as ready for any policies that has a solving mechanism in this energy crisis.

Determination of beta attenuation coefficients by means of timing method

Using a counting system with plastic scintillation detector, beta linear and mass attenuation coefficients were determined for bakelite, Al, Fe and plexiglass absorbers by means of timing method. To show the accuracy and reliability of the obtained results through this method, the coefficients were also found via conventional energy method. Obtained beta attenuation coefficients from both methods were compared with each other and the literature values. Beta attenuation coefficients obtained through timing method were found to be compatible with the values obtained from conventional energy method and the literature.

Redundant Reactions of Indeterminate Beams by Principle of Quasi Work

A new methodology for determining redundant reactions of beams is presented in this paper. This methodology is based on the principle of quasi work, which is a powerful pseudoenergy theorem deduced from Tellegen's theorem. It takes topography of a structural system as a variable in addition to the variables involved in conventional energy methods, variational principles, and finite element methods. The concept of topologically similar system lies at the heart of the principle of quasi work. This concept is explored for beams to define topologically similar beams and topologically equivalent beams. The principle of quasi work is validated for beams and subsequently used for determining redundant reactions of indeterminate and continuous beams. Further, a unique concept of reference beam is developed. Equation of deflection curve of this reference beam is used to solve redundant reactions of indeterminate beams. This methodology has an advantage of calculating redundant reactions mostly by simple multiplications without any integrations or differentiations and does not require any prior knowledge of writing bending moment expressions. The method is illustrated through examples. It is possible to develop an interactive graphic computer package for calculating reactions of indeterminate beams.

Relaxation on the energy method for the transient Rayleigh–Bénard convection

The onset of buoyancy-driven instability in initially quiescent fluid layers having the various boundary conditions is analyzed by using the energy method. New energy stability equation is derived under the Boussinesq approximation and the relative stability concept. The predicted critical conditions are compared with the previous results based on the conventional energy method. The stability limits which are related to the onset time of instabilities are presented as a function of the Rayleigh number Ra and the Prandtl number Pr. The present stability results predict that the onset time of convective instability decreases with increasing Ra and Pr. For the case of high Ra, the onset time of the instability is relatively insensitive to the boundary conditions of the upper boundaries.

Relaxed energy stability analysis on the onset of buoyancy-driven instability in the horizontal porous layer

The onset of buoyancy-driven instability in an initially quiescent, isotropic fluid-saturated porous layer is analyzed theoretically. Darcy’s law is employed to examine characteristics of fluid motion under the Boussinesq approximation. The critical condition to mark the onset of convective instability is analyzed based on the relaxed energy method. The predicted critical conditions are compared with the various results based on the conventional energy method and the linear stability theory.

Computation of cascade flutter by uncoupled and coupled methods

A computational method for flutter prediction of turbomachinery cascades is presented. The flow through multiple blade passages is calculated using a time-domain approach with coupled aerodynamic and structural models. The unsteady Euler/Navier-Stokes equations are solved in quasi-three-dimensions using a second-order implicit scheme with dual time-stepping and a multigrid method. A structural model for the blades with bending and torsion degrees of freedom is integrated in time together with the flow field. Information between structural and aerodynamic models is exchanged until convergence in each real-time step. Computational results for a cascade are presented and compared with those obtained by the conventional energy method and with experimental and numerical data by other authors. Significant differences are found between the coupled and uncoupled methods at low mass ratios. A transonic test case with strong nonlinear phenomena is investigated with the fluid-structure coupled method. Results for inviscid flow are compared with results of Navier-Stokes computations.

A stiffness derivative finite element technique for determination of crack tip stress intensity factors

A finite element technique for determination of elastic crack tip stress intensity factors is presented. The method, based on the energy release rate, requires no special crack tip elements. Further, the solution for only a single crack length is required, and the crack is “advanced” by moving nodal points rather than by removing nodal tractions at the crack tip and performing a second analysis. The promising straightforward extension of the method to general three-dimensional crack configurations is presented and contrasted with the practical impossibility of conventional energy methods.