Direct Instantaneous Torque and Axial Force Control Method for Linear-Rotary Switched Reluctance Motor with Two Radial Windings

IEEEDual-winding linear-rotary switched reluctance motors (LRSRMs) suffer from large torque ripple and severe coupling between the torque winding and the axial-force winding. To address these issues, this paper proposes a direct instantaneous torque and direct axial force control (DITC&DAFC) method to suppress torque ripple and reduce the impact of the coupling between two sets of windings. The DITC&DAFC method divides inductance-rising zone and inductance-falling zone according to the inductance characteristics, and uses hysteresis control to directly control the motor\u27s instantaneous torque in different intervals. Therefore, the generation of negative torque is reduced, which effectively suppresses torque ripples. Meanwhile, the method obviates the calculation of current and flux linkage, thereby alleviating the demands on the controller. In addition, the mechanical structure and operating mechanism of 6/4 pole LRSRM with two radial windings are described in detail. The feasibility of the proposed control method is verified through simulation and experimental results

Phase Commutation Optimized Control for Linear-Rotary Switched Reluctance Motor

IEEEThe traditional DTC method directly controls the torque and flux linkage without model calculation, which is beneficial to restraining torque ripples. However, the LRSRM not only provides the torque required for rotary motion, but also provides the axial force required for linear motion. Hence, the winding usually works in two-phase excitation mode. Given the different torque output capabilities of the front and rear phases under different rotor position angles, the conduction angles of the adjacent two phases can be further optimized. In this paper, a phase commutation optimized method is proposed to improve the torque generation between two neighboring phases and reduce torque ripple. Firstly, the hysteresis-loop control of the flux linkage is removed, which can reduce the calculation burden of digital controller. Secondly, the sector division and voltage vector selection without flux hysteresis control are redesigned. Experimental results verify the effectiveness of the proposed method. The phase current in negative torque region is reduced, and the torque ripple is suppressed as well

Work Function of Single-wall Silicon Carbide Nanotube

Using first-principles calculations, we study the work function of single wall silicon carbide nanotube (SiCNT). The work function is found to be highly dependent on the tube chirality and diameter. It increases with decreasing the tube diameter. The work function of zigzag SiCNT is always larger than that of armchair SiCNT. We reveal that the difference between the work function of zigzag and armchair SiCNT comes from their different intrinsic electronic structures, for which the singly degenerate energy band above the Fermi level of zigzag SiCNT is specifically responsible. Our finding offers potential usages of SiCNT in field-emission devices.Comment: 3 pages, 3 figure

Heavy Pentaquarks

We construct the spin-flavor wave functions of the possible heavy pentaquarks containing an anti-charm or anti-bottom quark using various clustered quark models. Then we estimate the masses and magnetic moments of the $J^P={1\over 2}^+$ or ${3\over 2}^+$ heavy pentaquarks. We emphasize the difference in the predictions of these models. Future experimental searches at BESIII, CLEOc, BELLE, and LEP may find these interesting states

An integrated method of feature extraction and objective evaluation of fabric pilling

A pilled fabric image consists of sub-images of different frequency components, and the fabric texture and the pilling information are in different frequency bands. Interference from fabric background texture affects the accuracy of computer-aided pilling ratings. A new approach for pilling evaluation based on the multi-scale two-dimensional dualtree complex wavelet transform (CWT) is presented in this paper to extract the pilling information from pilled fabric images. The CWT method can effectively decompose the pilled fabric image with six orientations at different scales and reconstruct fabric background texture and pilling sub-images. This study used an energy analysis method to search for an optimum image decomposition scale and dynamically discriminate pilling image from noise, fabric texture, fabric surface unevenness, and illuminative variation in the pilled fabric image. For pilling objective rating, six parameters were extracted from the pilling image to describe pill properties. A Levenberg-Marquardt backpropagation neural rule was used as a classifier to classify the pilling grade. The proposed method was evaluated using knitted, woven, and nonwoven pilled fabric images photographed with a digital camera.<br /

Pentaquark Magnetic Moments In Different Models

We calculate the magnetic moments of the pentaquark states from different models and compare our results with predictions of other groups.Comment: 17 pages, no figur

Magnetic Moments of JP=3/2+J^P={3/2}^+ Pentaquarks

If the $J^P$ of $\Theta_5^+$ and $\Xi_5^{--}$ pentaquarks is really found to be ${1\over 2}^+$ by future experiments, they will be accompanied by $J^P={3\over 2}^+$ partners in some models. It is reasonable to expect that these $J^P={3\over 2}^+$ states will also be discovered in the near future with the current intensive experimental and theoretical efforts. We estimate $J^P={3/2}^+$ pentaquark magnetic moments using different models.Comment: 13 page

Temperature - pressure phase diagram of the superconducting iron pnictide LiFeP

Electrical-resistivity and magnetic-susceptibility measurements under hydrostatic pressure up to p = 2.75 GPa have been performed on superconducting LiFeP. A broad superconducting (SC) region exists in the temperature - pressure (T-p) phase diagram. No indications for a spin-density-wave transition have been found, but an enhanced resistivity coefficient at low pressures hints at the presence of magnetic fluctuations. Our results show that the superconducting state in LiFeP is more robust than in the isostructural and isoelectronic LiFeAs. We suggest that this finding is related to the nearly regular [FeP_4] tetrahedron in LiFeP.Comment: 4 pages, 4 figure