Excitations In Poly Research Articles

Symmetry Breaking-Induced Resonance Dynamics in Bloch Point Nanospheres: Unveiling Magnetic Volume Effects and Geometric Parameters for Advanced Applications in Magnetic Sensing and Spintronics.

This study explores the impact of symmetry breaking on the ferromagnetic resonance of Bloch point (BP) nanospheres. Through standard Fourier analysis, we unveil two distinct oscillation mode groups characterized by low and high frequencies, respectively. Our findings emphasize the pivotal role of magnetic volume in shaping resonance amplitudes, providing new insights into the intricate dynamics of BP states. The investigation of geometric parameters reveals a quasi-monotonic decrease in resonance frequencies as a function of the asymmetry degree attributed to symmetry-breaking induced by geometric modifications. Spatial distribution analysis showcases unique resonance frequencies for the upper and lower BP hemispheres, highlighting the nuanced impact of the geometry on mode excitation. As the radius increases, additional modes emerge, demonstrating a compelling relationship between the magnetic volume and frequency. Phase analysis unveils coherent oscillations within each BP hemisphere, offering valuable insights into the rotational directions of the excitation poles. Beyond fundamental understanding, our study opens avenues for innovative applications, suggesting the potential use of nanospheres in advanced magnetic sensing, data storage, and nanoscale spintronic devices.

Adaptive-SMO-Based Traction Force Fluctuation Suppression Strategy Considering Suspension System for High-Speed Maglev Train

The excitation pole of the long stator linear synchronous motor (LSLSM) used to drive the high-speed maglev train is also used as the suspension electro-magnet, which makes the adjustment of the suspension system affect the excitation flux linkage of the motor when the train is running at high speed, resulting in significant non-periodic traction force fluctuations. This paper proposes a traction force fluctuation suppression strategy based on the flux linkage observation. First, based on the mathematical model of the LSLSM in double feed (DF) mode, the voltage equation based on the new extended back-EMF (NEEMF) is derived, which is less sensitive to the changes of parameters, load current, and speed, so that the flux linkage can be estimated more accurately. Then, to meet the high dynamic requirements of flux linkage observation at high speed, a sliding mode flux linkage observer (SMFO) is designed and a design method of the adaptive sliding mode gain is proposed to achieve fast convergence of the system. Finally, the stator reference current required to suppress the traction force fluctuation is calculated. Hardware-in-the-loop (HIL) expe-riments verify the effectiveness of the strategy.

Kendali Kecepatan Switched Reluctance Motor Berbasis FPGA

-- Renewable drive technology is developing in the current era, one of which is electric transportation. The Switched Reluctance Motor (SRM) was chosen for the transportation development because it has many advantages, including not using permanent magnets and simple construction in the form of an iron core in the rotor and stator windings. SRM works based on the reluctance phenomenon, namely, if the stator is energized, the stator will attract the nearby rotor, this is based on the tendency of the rotor poles to align with the stator excitation poles. SRM requires high speed switching control to operate and requires correct rotor position to operate. Maximum switching and good accuracy can use Field-Programmable Gate Array (FPGA) and rotary encoder as input for rotor position information. To use SRM in electric transport, it is necessary to adjust the speed with ease and precision. With the Pulse Width Modulation (PWM) technique, the size of the excitation depends on the size of the current, the size of the current is determined by the input voltage to the SRM. In this control, the PWM width can be changed by setting the carrier set and modulation set in the FPGA program. In this study, it is proposed to control the SRM speed by adjusting the PWM of the rotary encoder to produce the desired RPM. To support the achievement of this research, hardware testing was carried out in the laboratory. Keywords-- Duty cycle, FPGA, PWM, Reluctance, Switched Reluctance Motor.

Design and Research of Vertical Cross Force Sensor

In this study, the piezomagnetic force sensor used in the electro-hydraulic lifting equipment of agricultural machinery is analyzed, and a vertical cross force sensor is proposed. The sensor has two excitation cores, which can detect the force at multiple shear planes at the same time. Compared with the cylindrical force sensor, the sensor has two excitation cores, and the magnetic field bias increases when the sensor is stressed. The two excitation poles are arranged vertically and crosswise, which can detect the force along the two excitation poles at the same time, which is more in line with the actual working conditions. The magnetic circuit of the sensor is analyzed and deduced. The static and dynamic performances of the sensor are analyzed by experiments. The results show that the sensitivity of the vertical cross force sensor is 2.732mV/kN, which is 277.35% higher than that of the cylindrical force sensor. The linearity of the vertical cross force sensor is 6.55%, which is 38.44% lower than that of the cylindrical force sensor. The accuracy and resolution of the vertical cross force sensor are 6.63% and 0.87kN. Compared with cylindrical force sensor, they have obvious improvement. Vertical cross force sensor has better static and dynamic performance.

Self-Consistent Auxiliary Density Perturbation Theory.

The working equations for the extension of auxiliary density perturbation theory (ADPT) to hybrid functionals, employing the variational fitting of the Fock potential, are derived. The response equations in the resulting self-consistent ADPT (SC-ADPT) are solved iteratively with an adapted Eirola-Nevanlinna algorithm. As a result, a memory and CPU time efficient implementation of perturbation theory free of four-center electron repulsion integrals (ERIs) is obtained. Our validation calculations of SC-ADPT static and dynamic polarizabilities show quantitative agreement with corresponding coupled perturbed Hartree-Fock and Kohn-Sham results employing four-center ERIs. The comparison of SC-ADPT hybrid functional polarizabilities with coupled cluster reference calculations yield semiquantitative agreement. The presented systematic study of the dynamic polarizabilities of oligothiophenes shows that hybrid functionals can overcome the pathological misplacement of excitation poles by the local density and generalized gradient approximations. Good agreement with experimental dynamic polarizabilities for all studied oligothiophenes is achieved with range-separated hybrid functionals in the framework of SC-ADPT.

Study on the electromagnetic fields of a novel small-angle transducer used in high-precision inertial sensors

PurposeMicrosyn signal generators have been used in high-precision inertial sensors for their good structural stiffness and high sensitivity. However, as the stator and the rotor of the microsyn are both constructed of silicon-steel laminations with high permeability, an extremely small non-concentricity between the stator and rotor of microsyn will cause two random reaction torques acting on the output axis. As a result, difficulty arises in compensating for these random reaction torques. This study aims to investigate the electromagnetic fields of a novel angular transducer characterized by high sensitivity.Design/methodology/approachBased on the operation principles of the new transducer, the output voltage is decided by the time rate of change of the net magnetic flux of each output pole. The transient analysis of the electromagnetic field of the transducer is carried out by ANSYS Maxwell-3D.FindingsThe distributions of the magnetic flux of the transducer’s interior and eddy current on the rotor are consistent with the results of theory analysis. Moreover, the leakage flux mainly distributes nearby the excitation poles. The novel small-angle transducer also possesses a remarkably low reaction torque and power loss.Practical implicationsStudy on the electromagnetic fields of the new transducer not only provides a powerful basis to further improve the precision of the new transducer but also expands the scope of applications of the new transducer.Originality/valueThis new transducer is not only characterized by a high sensitivity, high linearity and fast response but also extremely low reaction torque and power losses. Thus, the new transducer is suitable for high-precision inertial sensors.

Analysis of a Novel Dual-Rotor Induction Motor for Pulsed Power Driving System

A novel dual-rotor induction motor (DRIM) is proposed as a potential substitution of the traditional motor/generator with a flywheel (MGFW) used in the pulsed power driving system (PPDS) which is especially deployed in mobile platforms. The DRIM is based on the integration of flywheel energy storage and electromagnetic slip coupling mechanism. The DRIM utilizes its outer rotor as a flywheel to store the input mechanical energy. By the interaction between the excitation field produced by the outer rotor and the eddy current induced on the surface of the inner rotor, an electromagnetic torque is generated and simultaneously acted on the two rotors. So the stored energy in the outer rotor can be directly transferred to the inner rotor with the mechanical load through the torque. The substitution of MGFW with DRIM holds potential for simplifying the PPDS and improving its compactness. The configuration and operation mechanism of the DRIM are firstly introduced in this paper. Then transient characteristics of the DRIM are analyzed by the 2D finite element method (FEM). The influences of the excitation pole number and the excitation coil turns on the performance of the DRIM are investigated. Finally, the feasibility of the DRIM is experimentally verified by a prototype.

E-Core Hybrid Reluctance Motor With Permanent Magnets Inside Stator Common Poles

In this paper, a new E-core hybrid reluctance motor (HRM) is proposed with permanent magnets (PMs), placed inside stator common poles. This motor is a 2-phase 12/16 HRM, which is characterized by a stator composed of four E-cores and a rotor with the same configuration of switched reluctance motors. The three poles of each E-core are identified as a common pole in the middle with no windings and two excitation poles in the sides with concentric windings. The windings of the excitation poles are wound such that both phases generate flux in the same direction as the PMs flux, so the demagnetization problem of the PMs is solved. The proposed motor is analyzed, and in order to illustrate the features and improvements, it is compared with two other well-established HRMs of the same size based on the simulation results obtained from the finite element analysis method. Moreover, some parameters like average torque, output power, and efficiency are compared, and it is illustrated that the proposed motor has better specifications compared to the other two. Finally, to verify the accurate design and operation of the proposed motor, its experimental verification is performed.

Design and analysis of a novel rotor-segmented axial-field switched reluctance machine

As excitation strategy is influenced by the parity of phase number, and serious end effect is caused by full pitch windings adopted by the conventional rotor-segmented switched reluctance machine (RS-SRM), a novel rotor-segmented axial-field switched reluctance machine (RS-AFSRM), which adopts concentrated windings, is proposed in this paper, whose control strategy is independent of the parity of phase number. The stator of the proposed RS-AFSRM consists of inner and outer flux-conductive ring, excitation poles, and stator yoke, while the rotor consists of fan-shape cylinder-type segments. The structure and principle of the proposed machine is introduced through the magnetic circuit model of the machine. The fringing effect on air-gap field is considered. The simplified magnetic circuit considering the fringing effect is presented and the fringing effect coefficient is introduced. The design procedure considering the fringing effect through iterative modification is presented in this paper and is validated through 3D finite-element method (3D-FEM). Results show that both magnetic field distribution and operation are reasonable and satisfy the requirements.

空間高調波を利用した自励式磁石フリーモータの回転子補極によるトルク特性改善

In this paper, a synchronous motor is described in which space harmonic power is utilized for field magnetization instead of permanent magnets. The stator has a concentrated winding structure, and the rotor has two different types of winding, i.e., an induction pole (I-pole) winding that primarily retrieves the second space harmonic and an excitation pole (E-pole) winding for the field magnetization. The two coils are connected via a center-tapped full-bridge diode rectifying circuit. The effects of the rotor electromangetomotive force distribution on the d- and q-axis are theoretically discussed. Then, the effect of the auxiliary poles is experimentally verified using a prototype motor in terms of the adjustable speed drive characteristics and the efficiency map. In addition, it is experimentally clarified that the rotor self-inductance and the rotor winding resistance significantly affect the conduction period of the rotor induced current.

Design and Analysis of a Permanent-Magnet-Assisted Switched Reluctance Motor

A permanent-magnet-assisted switched reluctance motor (SRM) having small excitation poles, where phase coils are concentrically wound on the poles and thin permanent magnets are inserted inside the poles, is proposed in this paper. The insertion of permanent magnets into the stator excitation poles has a significant influence on positive torque improvement leading to a boost in efficiency. Three key design parameters such as the thickness of permanent magnets, space between two adjacent permanent magnets, and the width of stator excitation poles are determined during a design procedure in terms of the enhancement of positive torque. Step-by-step design modification and a comparison between the proposed permanent-magnet-assisted SRM and no-permanent-magnet SRM have been conducted by means of static torque comparison along with dynamic performance. The first prototype from steel laminations up to its physical assembly has been constructed.

Torque Performance Improvement with Modified Rotor Winding Circuit of Wound-Field Synchronous Motor Self-Excited by Space Harmonics

This paper describes a synchronous motor in which space harmonic power is utilized for field magnetization instead of permanent magnets. The stator has a concentrated winding structure, and the rotor has two different types of windings, i.e., an induction pole (I-pole) winding that primarily retrieves the second space harmonic, and an excitation pole (E-pole) winding for field magnetization. The two coils are connected via a center-tapped full-bridge diode rectifying circuit. The optimum placement of the I-pole on the rotor is mathematically discussed and is analytically determined through FEM-based computer simulations. In addition, it is clarified that the E-pole torque increases owing to the effect of auxiliary poles. Further, the advantages of auxiliary poles are studied, using the torque ripple characteristics.

Correction to “Generation and Recombination Kinetics of Optical Excitations in Poly(3-dodecylthienylenevinylene) with Controlled Regioregularity”

Correction to “Generation and Recombination Kinetics of Optical Excitations in Poly(3-dodecylthienylenevinylene) with Controlled Regioregularity”

Levitation force analysis of medium and low speed maglev vehicles

The rule of levitation force variation with different structure and electromagnetic parameters provides a basis for electromagnet design of electromagnetic suspension (EMS) medium and low speed maglev vehicles. In order to acquire accurate calculation results of levitation force, different calculation methods, including analytical method, 2D FEM (finite element method), and 3D FEM, are applied to investigate the impact of various structural parameters, such as excitation current, air gap, lateral offset, and pole width, on levitation force. The analytical analysis is based on the classic mathematical model of levitation force between electromagnet and rail and performed with MATLAB. In the 2D and 3D FEMs, the numerical calculation of the levitation force is conducted with Ansoft by taking the magnetic saturation into account. In addition, the longitudinal end effect on the levitation force calculation is considered in the 3D FEM. The results show that the 3D FEM is the most accurate among the above three methods for calculating the levitation force, and the analytical method can only work for small current and/or large air gap conditions. A lateraloffset between vehicle and rail will reduce the levitation force; the levitation force descends sharply once the lateral offset exceeds the threshold, i.e., 8% of the pole width for U-shaped electromagnets. The maximum lift-to-weight ratio emerges when the pole width ratio of F type rail to electromagnet is 6:7. This may offer a reference for EMS maglev vehicle design and application.

Generation and Recombination Kinetics of Optical Excitations in Poly(3-dodecylthienylenevinylene) with Controlled Regioregularity

Regioregularity in π-conjugated polymers is known to have desirable effects on chain organization in the solid state leading to improved characteristics for electronic device applications. In this report, we studied the photophysics of a new series of π-conjugated polymers, namely, poly(3-dodecylthienylenevinylene), with controlled regioregularity (PTV-CR), using the steady state photoinduced absorption (PIA), doping-induced absorption (DIA), thermally modulated absorption (TMA), and photoluminescence (PL) techniques in a broad spectral range, as well as Grazing incidence X-ray diffraction (GIXRD). PTV-CR has a low band gap of 1.65-1.70 eV from the most random PTV-5:5 to regular PTV-0:10. We have found that regioregularity affects optical properties of PTV-CR in different ways than in the case of well-studied poly(3-alkylthiophene). We discovered that even the most random PTV-5:5 shows submicrometer crystalline order, and there is no correlation between regioregularity and crystallinality. We found that PTV is intrinsically dark due to the reverse order of 1B(u) and 2A(g) excitons, with PL quantum efficiency ranging from 10(-5) to 2 × 10(-4). Spectroscopic data confirm the existence of long-lived neutral (triplets) and charged (polaron) excitations, and thus PTV is a unique nondegenerate ground state π-conjugated polymer which is intrinsically nonluminescent. The recombination mechanism and lifetime of such long-lived excitations are investigated through the pump intensity and pump frequency dependencies as well as temperature dependence of the sample. Increasing regioregularity is seen to reduce the thermal responsivity and intersystem crossing in these films. The novel, intrachain character of these effects and their implications for use of PTV derivatives for photovoltaic application are discussed.

Ultrafast excited-state dynamics of RNA and DNA C tracts

The excited-state dynamics of the RNA homopolymer of cytosine and of the 18-mer (dC) 18 were studied by steady-state and time-resolved absorption and emission spectroscopy. At pH 6.8, excitation of poly(rC) by a femtosecond UV pump pulse produces excited states that decay up to one order of magnitude more slowly than the excited states formed in the mononucleotide cytidine 5′-monophosphate under the same conditions. Even slower relaxation is observed for the hemiprotonated, self-associated form of poly(rC), which is stable at acidic pH. Transient absorption and time-resolved fluorescence signals for (dC) 18 at pH 6.8 are similar to ones observed for poly(rC) near pH 4, indicating that hemiprotonated structures are found in DNA C tracts at neutral pH. In both systems, there is evidence for two kinds of emitting states with lifetimes of ∼100 ps and slightly more than 1 ns. The former states are responsible for the bulk of emission from the hemiprotonated structures. Evidence suggests that slow electronic relaxation in these self-complexes is the result of vertical base stacking. The similar signals from RNA and DNA C tracts suggest a common base-stacked structure, which may be identical with that of i-motif DNA.

A Linear Motor Design Provides Close and Secure Vehicle Separation of Many Transit Vehicles on a Guideway

Automated urban transit systems have been proposed for some time with limited attention to propulsion and control of many vehicles on a guideway. This is a particular critical requirement for personal rapid transit systems and an urban maglev transit system proposed by MagneMotion, the M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . The linear synchronous motor (LSM), as proposed for M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , has severe limitations. A modification of LSM is described, called "individual pole excitation linear motor" (IPELM), to meet the requirements of M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . The armature of IPELM consists of individual coils, incorporated in the guideway, which are powered separately under central control. An outline of IPELM design is presented for consideration and further development. Safety issues are reviewed for this linear motor. The main advantage of IPELM over LSM is the ability to control many vehicles on the same guideway with a very short headway and space between vehicles. A further development of IPELM makes it possible to design a continuous nonstop transit system with a high schedule speed between many online stations

Modelling and construction of a compact 500 kg HTS magnetic bearing

The progress of heavy-load HTS bearings depends on improvements in design,material quality and reliable cooling. We have constructed, manufacturedand tested a 200 mm HTS journal bearing with a thermally encapsulatedYBCO ring. For maximum force the larger gap due to the bearing cryostat(>4 mm) requires adjustment of the magnetic excitation pole distance and the Fe collector shimthickness. HTS material progress is obtained by top-seeded single- or multiple-grain growth whichincreases the averaged trapped magnetic flux density. Successful YBCO ring growth with radialc axis distribution by seeding the inner ring surface has been performed. The encapsulationensures a substantially reduced cryogenic effort and stabilizes bearing operation at 78–79 K.

Performance prediction of a hybrid-excitation synchronous machine with axially arranged excitation poles and permanent-magnet poles

This paper presents a method of predicting the steady-state performance of a new hybrid-excitation synchronous machine (HESM) theoretically. The field pole of this HESM is axially divided into two parts; one is an excitation part and the other a permanent-magnet (PM) part. A nonlinear equivalent circuit, which can include the saliency of the rotor and the magnetic saturation due to the iron core, is derived. Based on this equivalent circuit, the steady-state performance of the HESM is calculated, and the results are confirmed through experiments. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(2): 43–49, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20033

Low-lying two-photon excitations in poly( p-phenylene vinylene) and its derivatives

We study the low-lying two-photon excited states in nonlinear optical processes in poly( p-phenylene vinylene) (PPV) and its derivatives. We find that, within the Pariser–Parr–Pople (PPP) model, the mA g state in (unsubstituted) PPV is exactly the lowest two-photon excited state (i.e., the 2 1 A g + state). Due to the breaking of charge-conjugation symmetry, the 2A g in substituted PPVs, originating from the 1 1 A g − , is weakly two-photon allowed, while the mA g has its origin from the 2 1 A g + , hence giving a strong peak in the two-photon absorption spectra.