Independent Excitation Research Articles

Solar Quadrupole in Tensor Description

The cyclic variations in the quadrupole component of the solar magnetic field is studied in tensor description. The results are consistent with the classical description of the quadrupole using spherical functions, and the mathematical apparatus of tensor algebra allows one to compare the observed changes in the magnetic quadrupole and the changes predicted by the dynamo theories. In conclusion, the quadrupole properties can be adequately described by solar dynamo models that assume deviations from the dipole symmetry without the independent excitation of the quadrupole symmetry modes.

Narrow Aperture Detection Electrodes ICR Cell with Quadrupolar Ion Detection for FT-ICR MS at the Cyclotron Frequency.

Ion signal detection at the true (unperturbed) cyclotron frequency instead of the conventional reduced cyclotron frequency has remained a formidable challenge since the inception of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Recently, routine FT-ICR MS at the true cyclotron frequency has become a reality with the implementation of ICR cells with narrow aperture detection electrodes (NADEL). Here, we describe the development and implementation of the next generation of these cells, namely, a 2xNADEL ICR cell, which comprises four flat detect and four ∼45° cylindrical excite electrodes, enabling independent ion excitation and quadrupolar ion detection. The performance of the 2xNADEL ICR cell was evaluated on two commercial FT-ICR MS platforms, 10 T LTQ FT from Thermo Scientific and 9.4 T SolariX XR from Bruker Daltonics. The cells provided accurate mass measurements in the analyses of singly and multiply charged peptides (root-mean-square, RMS, mass error Δm/m of 90 ppb), proteins (Δm/m = 200 ppb), and petroleum fractions (Δm/m < 200 ppb). Due to the reduced influence of measured frequency on the space charge and external (trapping) electric fields, the 2xNADEL ICR cells exhibited stable performance in a wide range of trapping potentials (1-20 V). Similarly, in a 13 h rat brain MALDI imaging experiment, the RMS mass error did not exceed 600 ppb even for low signal-to-noise ratio analyte peaks. Notably, the same set of calibration constants was applicable to Fourier spectra in all pixels, reducing the need for recalibration at the individual pixel level. Overall, these results support further experimental development and fundamentals investigation of this promising technology.

A Mathematical Model of a Collector Traction Motor with Separate Consideration of Eddy Currents of the Main and Additional Poles

A mathematical model of a collector traction motor with independent excitation has been proposed in which eddy currents from the main and additional poles are separately taken into account. The results of computer simulations to determine the response of developed model to an abrupt change in the voltage across the anchor and when the anchor is powered by a pulse converter have been considered. The electromagnetic processes that occur in the traction motor have been examined in detail at rated and reduced current of main poles and at various speeds. The mechanism of the effect of eddy currents from additional poles on the magnetic flux of main poles of the machine, emf, and rate of rise of the anchor current has been analyzed. The factors directly affecting the degree of influence of eddy currents from additional poles on the electromagnetic processes in a traction motor have been determined. Conclusions have been drawn regarding the appropriateness of taking into account the phenomenon under consideration when simulating the operation of a traction electric drive.

Error estimation and enhanced stiffness sensitivity in contact resonance force microscopy with a multiple arbitrary frequency lock-in amplifier (MAFLIA)

In contact resonance force microscopy and related dynamic atomic force microscopy methods, an accurate description of the real-time cantilever dynamics is essential to the mapping of local material properties, such as viscoelasticity, piezo response, and chemical composition. Stiffness and damping variations of the tip-sample contact result in variations in the cantilever’s resonance frequency and quality factor as it scans a sample of interest. When measuring characteristics of the resonance, generally, there is a tradeoff between full spectral coverage, best obtained by sweeping the amplitude versus frequency response in the time or frequency domain, and high-speed information, obtained by observing the cantilever response at one or two discrete frequencies, that may be required to track a resonance frequency that changes spatially. Here, we introduce a new option for performing contact resonance force microscopy with a low-cost multifrequency lock-in amplifier system with up to eight simultaneous independent excitation and detection frequencies. We demonstrate how the multifrequency approach can measure contact resonance frequency, quality factor, amplitude, and phase during imaging, with high precision and error estimation, without the need for frequency-tracking feedback. We show, using a wood composite sample, that this multifrequency approach can determine resonance frequency and quality factor, and associated uncertainty. This ability to estimate uncertainty of resonance parameters is not possible with 1 and 2 frequency methods. We further utilize the multifrequency lock-in to develop a novel means of increasing the stiffness range for highly sensitive nanomechanical sensing by dividing the eight lock-in frequencies to monitor two or four simultaneous eigenmodes, each of which is optimized for sensitivity in a particular stiffness regime. Overall, we show how multifrequency lock-in amplifiers with observation frequency chosen to coincide with an expected eigenmode’s contact resonance can benefit the characterization of strongly heterogeneous samples, while maintaining fast measurement speed.

Power Experimental Optimization of Horizontal Axis Wind Turbine

Background: The presented article is a contribution to the realization of a wind emulator based on a continuous-current machine. The development of this topic focuses on the modeling of a vertical axis wind turbine, a DC motor with independent excitation and its control via a chopper. Methods: To carry out this work, we have studied and designed the electronic and mechanical sensors as well as a command implemented on the dSPACE DS1103 system. Results: The main purpose of this work is related, on one hand, to the control of the motor turbine by imposing the wind profile and on the other hand generate the command of the implanted MPPT. The experimental results obtained showed the great performances which characterize this improved wind energy system. Conclusion: Finally, a wind turbine with variable speed is a system having a complex model; however, a detailed model of the interaction between the wind and the aero-turbine is useful to understand certain phenomena such as rotational sampling or the spatial filter.

A Control System of an Electric Drive with a Synchronous Reluctance Machine with Independent Excitation

A method for adjusting frequency-regulated drives with the synchronous reluctance machine with independent excitation is proposed using the KhPT-250 cold tube reducing mill and traction drive of a Gazelle-Next electric vehicle as example; the method consists in independent adjustment of the phase currents with the subsequent identification of parameters of the control object by methods of frequency identification. It has been shown that, with independent control of the excitation currents and the anchor reaction, the cross links between phase current control loops can be neglected, which can be accounted for by the large bandwidth of the uniform pass-through frequency of the phase current control loops and the weak influence of phase windings located in the interpolar gap on the operation of the phase windings that currently located above the pole. It has been shown that when the drive operates at high speeds, a significant decrease in the proportionality coefficient between the magnitude of the electromagnetic moment and current is observed, which is explained by the finite speed of the phase current control loop. When adjusting the electric drive control system with dual-zone speed control, it has been suggested to introduce a correction for the anticipatory effect of the phase current in order to provide a constant relationship between the anchor component of phase current and the magnitude of electromagnetic moment.

A mini-review on recent progress of new sensitizers for luminescence of lanthanide doped nanomaterials

Trivalent lanthanide (Ln3+) doped luminescent nanocrystals are promising for applications ranging from biosensor, lasing, super-resolution nanoscopy, information security and so on. Although the utility prospect is of great attractions, the light absorption of these lanthanide doped nanocrystals is inherently weak due to the electric dipole-forbidden 4f → 4f transitions. Even worse, the quantum yields of upconverison nanocrystals are very low, which will unavoidably hinder their further applications. In a typical lanthanide luminescent nanosystem, both sensitizers as light absorption centers and activators as light emitting centers are necessary and important for desired luminescence properties. Among various sensitization systems, only Yb3+ and Nd3+ are considered as the most efficient sensitizers. Thus, the corresponding excitation wavelengths are strictly limited around 980 and 808 nm. To enrich excitation wavelengths and boost luminescence intensity, exploring more sensitization units that possess larger absorption cross section, higher efficiency of energy transfer process and independent excitation is imperative and beneficial for the demands of different applications, such as broadened absorption in near infrared (NIR) region for higher conversion efficiency of solar cells, prolonged excitation wavelength to second near infrared windows region (NIR II, 1,000–1,700 nm) for in vivo fluorescence imaging with deeper tissue depth and higher spatial resolution, more orthogonal excitations and emissions to improve optical multiplexing, and so on. Therefore, in the review, we primarily conclude several major energy transfer mechanisms from sensitizers to activators. Then we present three kinds of sensitizers, including lanthanide ions, organic dyes and quantum dots (QDs), and introduce the newly designed sensitization system that allows us to exploit superior excitation wavelength and amplify luminescence intensity. Finally, several future challenges and opportunities for the sensitizing strategies are discussed in hope of directing and broadening the applications of lanthanide nanosystem.

Optimization of Combined Braking of DC Motor of Independent Excitation

It is shown that the combined braking of a DC motor of independent excitation, combining the dynamic mode and the opposition mode, reduces the stopping time by 1.82 times compared with dynamic braking and by 1.63 times compared with the braking of the polarity reversal. Based on the analysis of the areas covered by the mechanical braking characteristics, a cubic equation is obtained, the solution of which gave the value of the switching speed from the dynamic mode to the polarity reversal mode, providing a minimum stop time. This expression contains two passport parameters of the engine - rated speed and rated coefficient of performance. The presented results are applicable for tuning the equipment of automatic control of an electric drive, providing a minimum braking time.

Перспективы применения на вагонах метрополитена системы независимого возбуждения тяговых машин

Перспективы применения на вагонах метрополитена системы независимого возбуждения тяговых машин

Torsional Oscillations and Damageability of the Rotor Shaft of the Turbogenerators Fitted with Automatic Regulated Excitation

The assessment of damage to the rotor shaft of the turbine-generator due to resonant interaction between generator and exciter, due to automatic excitation regulator (ARV) by mathematical modeling. The thyristor system of independent excitation is used in the work. The simulated circuit includes a turbogenerator with a block transformer, a power line, a synchronous generator and a gate-controlled exciter Converter. When modeling the electrical part, an approach is used from the position of its own coordinates, which provides maximum methodological consistency of the models of the listed devices and allows directly reproducing resonant phenomena at frequencies of torsional vibrations with the determination of instantaneous values of currents, voltages and electromagnetic moments of the turbo generator and exciter. The mechanical system is presented taking into account the exciter as a six-mass system. ARV is introduced into the mathematical model by means of transfer functions with corresponding coefficients and time constants. The control system of the gate Converter of the exciter is represented in the model by a generator of linearly increasing signals, a body for comparing these signals with the signal from the ARV and a control pulse generator. The deformation criterion for soft and hard loads in the zone of low-cycle fatigue and the force criterion in the zone of multi-cycle fatigue were used to assess the damage. A comparative quantitative assessment of the damage to the generator rotor shaft under resonant interaction at all subsynchronous frequencies of torsional vibrations and in near-resonant modes is given. The influence of attenuation of electromagnetic transients and damping of torsional vibrations on the damage values is analyzed.

Деполяризация субэпикарда предсердий крыс с экспериментально вызванной лёгочной гипертензией

Using an experimental model of pulmonary hypertension in rats (monocrotaline in a dose of 60 mg/kg), we revealed an additional focus of early excitation in the zone where the pulmonary veins enter the left atrium, in addition to the main focus in the sinoatrial node. Pulmonary hypertension leads to the formation of regions of early activation in the right and left atria and a significant change in the sequence of atrial depolarization. Propagation of independent excitation waves in the right and left atria increases heterogeneity of depolarization and leads to the formation of atrial arrhythmias.

Characterization of a Multiport Coaxial Line Adaptor for Multimodal Waveguides

A technique for the characterization of a class of coaxial-line-to-waveguide adaptors, which is based on the eigenvalues and eigenvectors of their scattering matrix, is presented. The adaptor comprises a number of coaxial-line ports symmetrically distributed on the surface of the waveguide. This allows for the independent excitation and measurement of different propagating modes in a multimodal operation. The latter is required for, e.g., the simultaneous determination of both constitutive parameters in microwave, millimeter-wave, and terahertz material characterization. It is shown that the junction is fully characterized in terms of the eigenvalues of its generalized scattering matrix. The measurement of these eigenvalues through a calibration procedure enables a complete characterization of the adaptor. A four-port coaxial-line adaptor was designed and fabricated. A modified calibration technique together with both measurements and electromagnetic simulations has been used for the determination of its scattering parameters.

QCT study of the vibrational and translational role in the H + C2H6(ν1, ν2, ν5, ν7, ν9 and ν10) reactions

Two important issues were analysed in the title reaction: the effects of vibrational excitation, associated with mode selectivity, and the role of translational energy, associated with Polanyi’s rules. Based on a global analytical potential energy surface, PES-2018, recently developed in our group, quasi-classical trajectory (QCT) calculations were performed at total energy of 35 kcal mol−1, either as translation or as a combination of translation and vibration energy. Independent vibrational excitation by one quantum of any of the CH3 stretching modes in ethane leads to similar dynamics pictures of reaction cross sections and H2(v′, j′) rotovibrational and scattering distributions, ruling out mode selectivity. Normal mode analysis showed a cold, non-inverted, H2(v′) product vibrational distribution, while the C2H5(v′) co-product presented many vibrational states, all of them with a low population, practically simulating a classical behaviour. An equivalent amount of energy as translation raises reactivity somewhat less effective than vibrational energy, contrary to that found for the O(3P) + CH4 reaction. Both reactions present “central” barriers, so this opposite behaviour shows the difficulties for a straightforward application of the Polanyi′s rules. The role of vibrational and translational energy on dynamics has been rationalized by the coupling between vibrational modes, which makes analysis of vibrational excitation difficult in polyatomic systems. Finally, the role of the total energy on reactivity and mode selectivity was analysed, concluding that at lower energy, 15 kcal mol−1, translational energy is much more effective than vibrational energy to enhance reactivity, while at intermediate energy, 20 kcal mol−1, the situation is more confusing and strongly dependent on the counting methods used in the QCT calculations. Therefore, very small mode selectivity is found, and translation seems to be more effective in enhancing reactivity than vibration at low collision energies, while this behaviour is reversed as we increase the collision energy, being the turning point around 20 kcal mol−1.

Design of electric drives with the improved mass-dimensional indicators for agricultural facilities

The article systematizes information on the structure of regulation of non-contact agricultural electric drives with improved mass-size parameters. Regulatory structures with independent control two-zone speed control and sequential excitation are proposed. It is shown that the best indicators are achieved in the scheme of sequential excitation and they reach values of 20-25%. Attention is drawn to the fact that structures with independent excitation are most relevant for dynamic mechanisms that realize the trajectory of motion with the maximum speed. Schemes of sequential excitation are most relevant for mechanisms with a large range of load variations on the motor shaft, for example, agricultural facilities. Schemes with two-zone speed control are most relevant for mechanisms that, with a large increase in speed, significantly reduce the load on the motor shaft.

Increased efficiency of tests of electric machines of various types

The paper describes the issues of operation of electric machines of various types. A wide adoption of asynchronous electric drives in various fields is noted. The relevance of the issue of embedding test complexes at companies conducting repairs, both asynchronous motors and direct current machines with different excitation types, is justified. The importance of the application modern power-saving technologies in the process of repair of electric machines is noted. One such technology is the method of mutual loading. Proposed scheme makes it possible to carry out tests by means of method of mutual loading such as induction motors, and direct-current machines with serial and independent (parallel) excitation. The effect is that the proposed scheme has a much lower cost compared to the total cost of schemes designed for testing of electric machines of the same types.

A New Hybrid Excitation Permanent Magnet Machine With an Independent AC Excitation Port

This paper proposes a novel hybrid excitation permanent magnet (PM) machine with an independent ac excitation port to extend the speed range and improve the torque capability. The proposed machine is characterized by an axial stator placed in one side of the rotor, which provides a shunted flux path of the radial stator. The prominent merit of the proposed machine is that it can make better utilization of the PM flux and offer a large flux regulation capability because the radial flux and the axial flux are in parallel to each other. Thorough analysis of the field distribution is performed by three-dimensional (3-D) finite-element analysis, and different operation modes of the proposed machine are illustrated and compared. Then, the flux regulation capability of the machine is analyzed using the simplified magnetic equivalent circuit, which is proved to give reasonable precision, indicating that the flux regulation ratio only depends on the design parameters of the ac excitation port. Finally, a 36-slot/six-pole prototype using the proposed configuration is built and tested. It is verified that the proposed machine exhibits excellent performance of flux regulation, thus offering a good potential to be used in wide-speed-range driving applications.

Analysis of operating modes of electric drives in agriculture

An algorithm for analyzing the operating modes of an agriculture electric machine as a control object based on its generalized mathematical model using the Fourier transform of non-sinusoidal signals of phase currents and conductance along the air gap of an electric machine is proposed, which is applicable to any electric machine with magnetic non-symmetry of rotor and which allows to obtain and investigate the spectral composition of such electric drive’s coordinates as induction and electromagnetic torque. According to such an algorithm, it is recommended to perform the calculation under the following assumptions: the machine is not saturated, the magnetic conductivity of steel is equal to infinity, there are no scattering fluxes. When going beyond these limitations, the calculation must be refined by a numerical finite element method using Maxwell’s equations. An example of an agriculture electric drive with a synchronous reluctance machine of independent excitation coordinates calculations is given according to the proposed algorithm in comparison with a numerical calculation by the finite element method.

Identification of Anchor Inertia Motor Moment of Direct Current and Loading in Experimental Vibration Installation for Chaotic Dynamics Study

Purpose of research. The article is devoted to development and approbation of parameters' assessment technique of anchor inertia moments of direct current motor with an independent excitation (DCM IE) and its loadings used in laboratory vibration installation for chaotic dynamics research.Methods. The DCM IE mathematical model and technique description for assessment of anchor inertia moment with loading as a result of parametrical identification on the basis of approximation integrated curve of current runaway and implementation of spectral analysis is described in the article. Joint dynamics modeling of Maxon RE25 electric motor with electric and mechanical part was done in Matlab Simulink system. Mechanical part was constructed in MSC Adams. Technique operability of parametrical identification was checked on the basis of machine experiment results.Results. Structure and general view of information and measuring system of laboratory vibration installation for chaotic dynamics research on the basis of input-output NI USB-6009 module is presented. Dispersal curves and an amplitude range of current received during experiment for definition of anchor inertia moments of Maxon RE25 engine and debalances are analysed. Calculation of anchor inertia moments and debalances are made according to an offered technique. Calculation of relative errors in comparison with passport value is also made.Conclusion. According to the results of carried out parallel experiments it is found out that experiments can be made according to Kokhren's criterion. And the error of DCM anchor inertia moments definition is no larger than 5%. Therefore it can also be used for calculations with sufficient accuracy of debalances inertia moments.

Online control of combine reel height in presence of farm roughness using an on-off controller

Adjusting the harvesting combine reel height in presence of the farm rough surface reduces the harvest losses, prevents possible damage to the headland and increases gravel harvest. Regarding the importance of the issue, in this study, the dynamics of the reel height control system of the John Deere1055 combine was modeled and the controllability and observability of the obtained transfer function is determined in state space. After that, with the aim of cutting the stem from a suitable point, an on-off controller is designed to keep the reel height from the ground in a permitted range. At this stage, a reduced model system is used as an approximated system to design a controller. The designed controller is simulated in MATLAB. In this simulation, the roughness of the ground was considered as the control loop noise with the normal probability distribution function. The results confirm that the reel height change is kept in the specified range against the farm roughness. The laboratory sample was also constructed using an independent excitation circuit DC motor, an optical distance sensor, and a micro controller. The experimental test shows that the height control system responses to changes in surface height at an appropriate speed without any oscillation in range.

Excitation and tuning of a dual graphene plasmonic wave based on a trapezoidal grating structure

The independent excitation and tuning of a dual-band graphene plasmonic wave are realized in a hybrid structure that consists of two graphene monolayers placed above and below the trapezoidal grating. Because of the transparency of graphene in the mid-infrared range, the incident light can travel through the first graphene layer to be diffracted by the grating structure and couple its energy to both graphene layers. Numerical simulations are performed using the finite difference time domain method. Results show that the plasmon resonances corresponding to the two graphene monolayers are excited at 9.8 and 10.9μm, which agrees well with the theoretical analysis. Because of the fast and efficient electrical tunability of graphene, the resonance wavelengths can be tuned individually by changing the chemical potential of the corresponding graphene. Furthermore, the effects of geometric parameters and the refractive index of the surrounding media are studied. The results show that the structure can achieve an optimal sensing coefficient at 0.4 and 0.5eV for the top and bottom graphene plasmon resonances, respectively. The proposed structure provides an alternative option to engineer the proposed structure for sensing with high detection accuracy at mid-infrared wavelengths.