Terms Of Harmonics Research Articles

Power Quality and Break-Even Points in the Use of Electric Motorcycles in the Case of the Thailand Residential Building

The use of electric motorcycles (EMCs) is rapidly increasing because EMCs are comparable in price to internal combustion engine motorcycles (ICE motorcycles), can be charged at home, and do not cause pollution. However, using EMCs in residential electrical systems is still a new issue in Thailand, as the Thai power grid was not originally designed to support electric vehicle charging. Therefore, the effect that may occur on the electrical system of a house should be studied. In this study, the power quality when charging an EMC in a residential electrical system is investigated by considering the circuits of various electrical devices according to their actual consumption behavior. Three electric motorcycles with battery capacities of 20, 30, and 40 Ah were used to investigate the effects of charging these motorcycles through the electrical system of a house. The experiment was conducted in a laboratory that replicated the electrical system of a house, and the conditions and patterns of power consumption were identical in all three cases. The test results were considered in terms of power quality, voltage harmonics, and current power system harmonics to analyze the effects on the electrical system in each circuit and to compare the charging differences of each motorcycle model. Next, it was determined that using an EMC is more cost-effective than using an ICE motorcycle. ICE motorcycles will eventually be completely replaced by EMCs, and our research will enable informed decision-making for electric motorcycle riders, researchers, and automotive corporations.

Analysis of the Influence of the 6-Pulse Thyristor-Bridge Input Reactor Size on the Shunt Active Power Filter Work Efficiency: A Case Study

This paper presents a case study in which the influence of the 6-pulse thyristor-bridge input reactor size on the shunt active power filter (SAPF)’s work performance is investigated. The purpose of using an SAPF in the power system is in most cases for fundamental harmonic reactive power compensation, harmonics and asymmetry mitigation. The work efficiency of such a filter depends not only on the designed control system, interface filter and dc-link capacitor parameters, but also on the parameters of the electrical system in which it is connected. Therefore, it is necessary to study and know the power system (supplier and consumer sides) before its installation. For instance, in the electrical system with diode or thyristor-bridge as loads, the SAPF performance efficiency may not be satisfied due to the high rate of current change (di/dt) at the points of commutation notches. In this paper, the performed simulation and laboratory experiments show that for a better operating efficiency of the SAPF, the input reactor parameters should be selected based not only on the effective reduction in the inverter switching ripple or the control system demand, but also on the parameters of the load, such as the parameters of the diode or thyristor-bridge input reactor. Apart from the experimental demonstrations on how the input reactor size influences the SAPF work efficiency, the novelties in this paper are: the formulated recommendations on how to choose the SAPF input reactor parameters (the SAPF is more efficient in terms of harmonics, asymmetry and reactive power mitigation when the inductance of its input reactor (L-filter) is smaller than the one of the diode or thyristor-bridge input reactor); the proposed SAPF control system; the proposed expressions to compute the SAPF input reactor inductance, DC voltage and capacitor.

Design and Implementation of an Electronic Fan Regulator for Reduced Harmonics and Ripple Free Speed

Majority electronic fan regulators available in the market feed significant amounts of harmonics into the fan, which leads to fan overheating and frequent failures of fan capacitors. This paper presents a design and development of a new electronic fan regulator that feeds negligible amounts of harmonics into the fan, and hence offers more reliable fan operation with smooth control and ripple free speed.The paper first reviews different forms of power electronic based control applicable to single-phase induction motors, and then identifies six topologies suitable for ceiling fans, based on the simplicity and cost effectiveness in meeting the performance targets. Final topology for the new design was selected after simulation of each short-listed topology to assess relative performances in terms of lesser harmonics, ripple free speed, smooth control, and cost. Finally, a prototype was built of the selected topology for a 70W single phase ceiling fan and test results verified the simulation results. Details of investigations, design, simulation, and test results are given and discussed.

Linguopragmatuics of EU Regulatory Documents on Migration Regulation Issues

The accelerating migration movements dictate the need to coordinate the efforts and policies of different states, this makes the issues of managing migration processes of particular relevance and importance. The migration crisis in Europe in 2015-2019 turned a serious challenge for the viability of the European Union itself. The acute phase of the most recent migration crisis forced the European Union to revise existing migration policies, with regard to both EU member states and to migrants heading to Europe. The present study focuses on an analysis of the vocabulary of EU official legal documents in order to identify the specificities of migration regulation during the acute phase of the migration crisis. The use of discursive, pragmalinguistic and content analyses shows that migration institutional discourse functions as a strong ideological tool that can be used not only to control hostile attitudes in society but also to minimize conflicts in the process of migrants’ integration. The specific linguistic techniques identified in the process of the analysis seem promising in terms of harmonisation of migration processes. The experience of the European Union may be of practical importance for Russia and the countries of the near abroad which also have encountered the migration problems. Therefore the understanding of approaches that contribute to the regulation of migration processes can help reduce the level of aggression in the countries of migrants acceptance.

Scattering of elastic waves by a sphere with orthorhombic anisotropy and application to polycrystalline material characterization

Scattering of elastic waves by an anisotropic sphere with orthorhombic symmetry inside an isotropic medium is studied and applied to characterization of polycrystalline materials with anisotropic grains. For a single sphere the waves in the isotropic surrounding are expanded in the spherical vector wave functions. Inside the sphere, the elastodynamic equations are first transformed to spherical coordinates and the displacement field is expanded in terms of the vector spherical harmonics in the angular directions and power series in the radial direction. The governing equations inside the sphere give recursion relations among the expansion coefficients in the power series. The boundary conditions on the sphere then determine the relation among the scattered wave expansion coefficients and those of the incident wave, expressed as the transition (T) matrix. For low frequencies the elements of the T matrix are obtained in explicit form. According to the theory of Foldy the T matrix elements of a single sphere are used to study attenuation and phase velocity of polycrystalline materials, explicitly for low frequencies. Comparisons of the present method with previously published results and recent FEM results show a good correspondence for low frequencies. The present approach shows a better agreement with FEM for strongly anisotropic materials in comparison with other published methods.

Pure/combined buckling mode calculation of thin-walled members constraining general shell FE models

This paper proposes a technique for decomposing the buckling solution of thin-walled members into pure deformation modes (global, distortional, local, or other), aiming at providing an insight into the buckling behavior of these members. The calculation of critical loads associated with a specific or combined deformation mode is performed constraining general finite element models. A general constraining procedure is presented, in which the critical load of any mode, combining different section deformation modes and different harmonic shape functions in the longitudinal direction, can be determined. Cases where all possible harmonic terms may be automatically considered are also described. Cross-section deformation modes are defined in the context of the constrained finite strip method (base vectors), and the proposed constraining procedure is implemented by means of relationships between degrees of freedom of the finite element mesh in commercial software. Calculation of combined buckling modes inherently makes it possible to quantify the participation of the considered modes, including along specific longitudinal segments of the member. Results from the analysis of a lipped channel member are presented to demonstrate the concepts and, later, the analysis of a member with a more complex cross-section and intermediate boundary conditions along length is detailed. A discussion on the base vectors chosen for the constraining method is presented. Finally, the potential of the proposed method is discussed.

Sound radiation of a vibrating circular plate set in a hemispherical enclosure

This study rigorously addresses the Neumann–Robin problem of sound radiation from a vibrating flexible disk embedded into a hemispherical enclosure. The enclosure is acoustically soft on its inside surface and hard on its outside surface. The method of superimposed solutions, expressed in terms of Dini series and spherical harmonics, has been applied for this purpose. The presented solution is applicable to any vibration velocity profile on the radiator, with an elastically supported thin plate excited asymmetrically used as an example. The results presented here can be valuable for modeling vibroacoustic responses of various speakers, sensors, and microphones with edges either clamped to the enclosure or nearly free. Achieving this involves modifying the values of the boundary stiffness for resisting transverse displacement and the rotation of the plate’s edge. Additionally, when applying these results to model the responses of alarm or signaling transducers, high-amplitude responses are expected for selected resonant frequencies. In such cases, the boundary stiffness values can be set to ensure multiple strong and wide resonant maxima in the frequency characteristics. In addition, the results presented in this study include solving the dynamic equation of motion for the plate or rigid piston with external excitation. This equation is coupled with the wave equation inside and outside the hemispherical enclosure, allowing the inclusion of the enclosure’s effect on the plate-enclosure system’s responses. This approach can be useful for modeling and improving the acoustic responses of spherical speakers. In such cases, the boundary stiffness values should be relatively small to emulate a soft suspension of the plate. The impedance of the enclosure’s internal surface can be arbitrarily selected, ranging from acoustically hard to acoustically soft. In this study, the impedance of mineral wool has been applied. Numerical analysis is presented for frequencies below 4kHz, with errors smaller than 0.2%. The results have been validated using the finite element method.

The effect of lamppost scatterers on direction finding by cylindrical arrays of dipoles intended for smart antenna application in wireless communications

Smart antennas are widely used to enhance the capacity of the wireless communication systems in urban areas. To enhance the capacity by increasing the signal to noise ratio, one should estimate the angle of arrival precisely. In urban areas, the scattering from the lampposts in a boulevard or a highway is not negligible and its effect should be considered in direction finding algorithms. In this paper the lampposts are modelled by thick and long cylindrical scatterers and the scattered electric field is computed in terms of the cylindrical harmonics analytically. Then the total electric field is evaluated to estimate the angle of arrival by MUSIC direction finding algorithm. The computed total electric field with the proposed method shows a good agreement with precise HFSS simulation results for different incident angles. Monte-Carlo simulations are conducted to evaluate the RMS error values using cylindrical array of dipole antennas for direction finding and the results show that the proposed method can model the effects of the finite number of the lampposts in a wireless propagation scenario adequately, with reduced burden of computations. This fact contributes to a better planning of the beamforming in smart antennas with corresponding resolution.

Research of integrated shimming Halbach magnet for High strength, compact Benchtop NMR device

Due to production and assembly errors of magnets resulting in reduced magnetic field homogeneity, passive shimming (PS) is necessary when Halbach magnets are used in high-resolution Benchtop Nuclear Magnetic Resonance (BNMR) spectrometer. The conventional PS technique, which places independent PS devices inside the magnet aperture, is no longer applicable to small-aperture compact high-field-strength Halbach magnet studies. In this paper, based on spherical harmonic function expansion, we improve the magnetic field homogeneity by optimizing the moving step of the magnet moving arrays composed of Halbach magnets to generate the corresponding harmonic terms to compensate for the magnetic field. With this approach, the homogeneity of a 1 T Halbach magnet was improved from the original 3913 ppm to 8 ppm in a L10 mm × R2.5 mm of 0.64% copper sulfate doped water sample. This work explores the PS mechanism based on the movement of magnetic blocks, which can be applied in BNMR and other compact high-field strength high-homogeneity Halbach magnets application circumstances.

The performance of hybrid and F12∗/F12c explicitly correlated coupled cluster methods for use in anharmonic vibrational frequency computations

AbstractA hybrid quartic force field approach produces the same accuracies as non‐hybrid methods but for less than one quarter of the computational time. This method utilizes explicitly correlated coupled cluster theory at the singles and doubles level inclusive of perturbative triples (CCSD(T)‐F12b) in conjunction with a triple‐ basis set, core electron correlation, and scalar relativity for the harmonic terms and CCSD(T)‐F12b with a valence double‐ basis set for the cubic and quartic terms. There is no sacrifice in the prediction of fundamental anharmonic vibrational frequencies or vibrationally‐averaged rotational constants as compared to experiment, but the time saved is notable. Other hybrid methods are examined involving different sizes of basis sets and composite terms included or excluded. Not one is more accurate; only one is faster. F12 (also called F12c) is tested as well, but it has an increase in computational time for no increase in accuracy. As such, this work reports a hybrid and composite approach (F12‐TcCR+DZ) in the computation of rovibrational spectral data which can be applied to the observation of novel molecules in the gas phase in the laboratory and potentially even in astrophysical environments.

Attractors' Analysis and Bifurcation Diagrams for an Impacting Inverted Pendulum in the Presence of a Two-Terms Harmonic Excitation

Abstract In this work, we examine the nonlinear dynamics of an inverted pendulum between lateral rebounding barriers. We continue the numerical investigation started in (Demeio et al., 2006, “Response Scenario and Non-Smooth Features in the Nonlinear Dynamics of an Impacting Inverted Pendulum,” ASME J. Comput. Nonlin. Dyn., 1(1), pp. 56–64) by adding the contribution of the second harmonic in the external forcing term. We investigate the behavior of the periodic attractors by bifurcation diagrams with respect to each amplitude and by behavior charts of single attractors in the amplitude parameters plane for fixed frequency. We study the effects of the second harmonic term on the existence domain of each attractor, on local bifurcations, and on the changes in the basins of attraction. The behavior of some robust chaotic attractor is also considered. In the evolution of the periodic attractors we have observed that the addition of the second harmonic generates a rich variety of behaviors, such as loss of stability and formation of isolas of periodic orbits. In the case of chaotic attractors, we have studied one attractor at high frequency, ω = 18, and one at low frequency, ω = 3. In the high frequency case we detect a transition from a scattered to a confined attractor, whereas at the lower frequency the chaotic attractor is present over a wide range of the second harmonic's amplitude. Finally, we extend the investigation of the chaotic attractors by bifurcation diagrams with respect to the frequency.

Decomposition of multi-particle azimuthal correlations in Q-cumulant analysis* *Supported by the Ministry of Education Science and Technological Development, Republic of Serbia, the National Natural Science Foundation of China (12035006, 12075085, 12147219), and the U.S. Department of Energy (de-sc0012910).

The method of Q-cumulants is a powerful tool for studying the fine details of azimuthal anisotropies in high energy nuclear collisions. This paper presents a new method, based on mathematical induction, to evaluate the analytical form of high-order Q-cumulants. The capability of this method is demonstrated via a toy model that uses the elliptic power distribution to simulate the anisotropic emission of particles, quantified in terms of Fourier flow harmonics . The method can help in studying the large amount of event statistics that can be collected in the future and allow measurements of the very high central moments of the distribution. This can, in turn, facilitate progress in understanding the initial geometry, the input to the hydrodynamic calculations of medium expansion in high energy nuclear collisions, and the constraints on it.

Assessment of Converter Performance in Hybrid AC-DC Power System under Optimal Power Flow with Minimum Number of DC Link Control Variables

This paper presents a strategy to evaluate the performances of converter stations under the optimized operating points of hybrid AC-DC power systems with a reduced number of DC link variables. Compared to previous works reported with five DC-side control variables (CVs), the uniqueness of the presented optimal power flow (OPF) formulation lies within the selection of only two DC-side control variables (CVs), such as the inverter voltage and current in the DC link, apart from the conventional AC-side variables. Previous research has mainly been focused on optimizing hybrid power system performance through OPF-based formulations, but has mostly ignored the associated converter performances. Hence, in this study, converter performance, in terms of ripple and harmonics in DC voltage and AC current and the utilization of the converter infrastructure, is evaluated. The minimization of active power loss is taken as an objective function, and the problem is solved for a modified IEEE 30 bus system using a recently developed and very efficient Archimedes optimization algorithm (AOA). Case studies are performed to assess the efficacy of the presented OPF model in power systems, as well as converter performance. Furthermore, the results are extended to assess the applicability of the proposed model to the allocation of photovoltaic (PV)-type distributed generations (DGs) in hybrid AC-DC systems. The average improvement in power loss is found to be around 7.5% compared to the reported results. Furthermore, an approximate 10% improvement in converter power factor and an approximate 50% reduction in ripple factor are achieved.

Quantum mechanics on time-varying space domains

The extension of quantum theory to time-varying space domains is often challenging, since domain evolution frequently results in non-autonomous and non-adiabatic evolution of corresponding wave function for a given quantum mechanical system. For generic domain evolution, we show that the evolution of the wave function is determined by the mixing of spatial modes or bound states, and this is the instigator for non-adiabatic wave function evolution. For some applications, it is desirable to retain adiabaticity of the wave function and with knowledge of how domain evolution causes loss of adiabaticity, we construct a control potential—comprising a harmonic term and a volume expansion/contraction term—which may be used to counteract this feature of domain evolution, thereby preserving wave function adiabaticity throughout the time evolution of the space domain. Examples of quantum mechanical systems on time-varying space domains are used to illustrate the theory, including analogues of classical examples such as the hydrogen atom and quantum harmonic oscillator on unbounded stretched space and a particle in a stretched and translated box. We also discuss how to combine our approach with numerical simulations, using the compressed hydrogen atom confined within an evolving sphere to demonstrate the method.

Modal Projection for Quasi-Homogeneous Anisotropic Turbulence

This article, or essay, addresses the anisotropic structure and the dynamics of quasi-homogeneous, incompressible turbulence. Modal projection and expansions in terms of spherical harmonics in three-dimensional Fourier space are in line with a seminal study by Jack Herring, around the so-called Craya–Herring frame of reference, with a large review of the related approaches to date. The research part is focused on structure and dynamics of rotating sheared turbulence, including a description of both directional and polarization anisotropy with a minimal number of modes. Effort is made to generalize expansions in terms of scalar spherical harmonics (SSHs) to vector spherical harmonics (VSHs). Looking at stochastic fields, for possibly intermittent vector fields, some directions are explored to reconcile modal projection, firstly used for smooth vector fields, and multifractal approaches for internal intermittency but far beyond scalar correlations, such as structure functions. In order to illustrate turbulence from Earth to planets, stars, and galaxies, applications to geophysics and astrophysics are touched upon, with generalization to coupled vector fields (for kinetic, magnetic, and potential energies), possibly dominated by waves (Coriolis, gravity, and Alfvén).

Calculating the fraction of Kawasaki disease potentially attributable to seasonal pathogens: a time series analysis.

Kawasaki disease is an acute, febrile, systemic vasculitis of children that primarily affects medium-sized blood vessels with a tropism for the coronary arteries. Although the etiological factors remain unknown, infections have been suggested as the trigger of Kawasaki disease. We sought to calculate the fraction of Kawasaki disease potentially attributable to seasonal infections. This cohort study used a population-based time series analysis from the French hospitalisation database (Programme de Médicalisation des Systèmes d'Information), which includes all inpatients admitted to any public or private hospital in France. We included all children aged 0-17 years hospitalised for Kawasaki disease in France over 13 years. The monthly incidence of Kawasaki disease per 10,000 children over time was analysed by a quasi-Poisson regression model. The model accounted for seasonality by using harmonic terms (a pair of sines and cosines with 12-month periods). The circulation of eight common seasonal pathogens (adenovirus, influenza, metapneumovirus, Mycoplasma pneumoniae, norovirus, rhinovirus, rotavirus, respiratory syncytial virus, and Streptococcus pneumonia) over the same period was included in the model to analyse the fraction of Kawasaki disease potentially attributable to each pathogen. Infections were identified on the basis of polymerase chain reaction or rapid antigen testing in hospital laboratories. Between Jan 1, 2007, and Dec 31, 2019, we included 10,337 children with Kawasaki disease and 442,762 children with the selected infectious diseases. In the Kawasaki disease cohort, the median age [IQR] was 2 [0-4] years, 6164 [59.6%] were boys. Adenovirus infection was potentially responsible for 24.4% [21.5-27.8] (p<0.001) of Kawasaki diseases, Norovirus for 6.7% [1.3-11.2] (p=0.002), and RSV 4.6% [1.2-7.8] (p=0.022). Sensitivity analyses found similar results. This cohort study of data from a comprehensive national hospitalisation database indicated that approximately 35% of Kawasaki diseases was potentially attributable to seasonal infections. None.

Exact solution of Dirac–Rosen–Morse problem in curved space–time

In this work, we extend the analysis of the relativistic Dirac–Rosen–Morse problem in curved space–time. For that, we consider the Dirac equation in curved space–time with line element d s2 = (1 + α2 U( r))2(d t2 − d r2) − r2dθ2 − r2sin 2θdϕ2, where α is fine structural constant, U( r) is a scalar potential, and in the presence of the electromagnetic field Aμ = ( V( r), cA( r), 0, 0). Because of the spherical symmetry, the angular spinor is given in terms of the spherical harmonics. For the radial spinor, we apply a unitary transformation and define the vector component of the electromagnetic field A( r) written as a function of V( r) and U( r) so as to solve the radial spinor for Dirac–Rosen–Morse problem. Graphical analyses were performed comparing the eigenenergies and the probability densities in curved and flat space–time to visualize the influence of curvature in space–time on the two-component radial spinor, with the upper and lower components representing the particle and antiparticle, respectively.

BEYONDPLANCK

We introduce a new formulation of theConviqtconvolution algorithm in terms of spin harmonics, and apply this to the problem of sidelobe correction for BEYONDPLANCK, the first end-to-end Bayesian Gibbs sampling framework for CMB analysis. We compare our implementation to the previousPlanckLevelS implementation, and find good agreement between the two codes in terms of accuracy, but with a speed-up reaching a factor of 3–10, depending on the frequency bandlimits,lmaxandmmax. The new algorithm is significantly simpler to implement and maintain, since all low-level calculations are handled through an external spherical harmonic transform library. We find that our mean sidelobe estimates forPlanckLFI are in good agreement with previous efforts. Additionally, we present novel sidelobe rms maps that quantify the uncertainty in the sidelobe corrections due to variations in the sky model.

The spatio-temporal distribution of acute encephalitis syndrome and its association with climate and landcover in Vietnam

BackgroundAcute encephalitis syndrome (AES) differs in its spatio-temporal distribution in Vietnam with the highest incidence seen during the summer months in the northern provinces. AES has multiple aetiologies, and the cause remains unknown in many cases. While vector-borne disease such as Japanese encephalitis and dengue virus and non-vector-borne diseases such as influenza and enterovirus show evidence of seasonality, associations with climate variables and the spatio-temporal distribution in Vietnam differs between these. The aim of this study was therefore to understand the spatio-temporal distribution of, and risk factors for AES in Vietnam to help hypothesise the aetiology.MethodsThe number of monthly cases per province for AES, meningitis and diseases including dengue fever; influenza-like-illness (ILI); hand, foot, and mouth disease (HFMD); and Streptococcus suis were obtained from the General Department for Preventive Medicine (GDPM) from 1998–2016. Covariates including climate, normalized difference vegetation index (NDVI), elevation, the number of pigs, socio-demographics, JEV vaccination coverage and the number of hospitals were also collected. Spatio-temporal multivariable mixed-effects negative binomial Bayesian models with an outcome of the number of cases of AES, a combination of the covariates and harmonic terms to determine the magnitude of seasonality were developed.ResultsThe national monthly incidence of AES declined by 63.3% over the study period. However, incidence increased in some provinces, particularly in the Northwest region. In northern Vietnam, the incidence peaked in the summer months in contrast to the southern provinces where incidence remained relatively constant throughout the year. The incidence of meningitis, ILI and S. suis infection; temperature, relative humidity with no lag, NDVI at a lag of one month, and the number of pigs per 100,000 population were positively associated with the number of cases of AES in all models in which these covariates were included.ConclusionsThe positive correlation of AES with temperature and humidity suggest that a number of cases may be due to vector-borne diseases, suggesting a need to focus on vaccination campaigns. However, further surveillance and research are recommended to investigate other possible aetiologies such as S. suis or Orientia tsutsugamushi.

Dirac equation in relativistic density functional theory and mapped Fourier grid method

For studying the electronic structure of solids consisting of heavy atoms, the Dirac–Kohn–Sham equation is considered in the presence of the Mathieu potential. The two-component spinors and the potential function are expanded in terms of spherical harmonics. Also, a numerical approach is presented to study the Dirac–Kohn–Sham equation in the presence of the noncentral Mathieu potential. Then, the energy eigenvalues and eigenvectors are obtained in the case of spherically expanded potential in the Brillouin zoon by using the mapped Fourier grid method.