Arc Width Research Articles

Widths of dayside auroral arcs observed at the Chinese Yellow River Station

Due to the altitudinal extent of an auroral arc, its observed width is different at different zenith angles even when its real width is the same. For that reason, former measurements of arc widths were obtained only for arcs located close to the geomagnetic zenith direction. A method to correct arc width is proposed in the paper, which considers the altitudinal extent of auroral arc. Then, we apply this method to the auroral arcs observed at the Chinese Yellow River Station, and analyze the widths of 17,571 dayside auroral arcs. The distributions of the widths are almost the same at different zenith angles with an average width of 18.5km. Arc widths are narrower as MLT is close to midday.

Simulation analysis of cogging torque of permanent magnet synchronous motor for electric vehicle

This paper proposes a new approach to study generation mechanism and influence factors of cogging torque of permanent magnet synchronous motors, in order to improve the operational performance and riding comfort of electric vehicle. Based on energy method and Fourier expansion, the method of predicting cogging torque is proposed. Two-dimensional finite element model of in-wheel motor is established by Maxwell software, and electromagnetic character of that is analyzed. Skew slot, pole arc coefficient and width of slot mouth are analyzed and studied by finite element method, in order to realize the change regularity of cogging torque. Cogging torque curves under the different skew slots, the different pole arc coefficients and the different widths of slot mouth are obtained, which can effectively reduce the cogging torque of in-wheel motor, but they still exists some limitations. The final simulation analysis results are in good agreement with the theoretical predicting results, which indicates that this method can be used to afford a theoretical basis to reduce the cogging torque and optimize the in-wheel motor of electric vehicle in the future.

Torque Ripple Reduction of a Direct-Drive Permanent-Magnet Synchronous Machine by Material-Efficient Axial Pole Pairing

This paper investigates a material-efficient axial pole pairing method for torque ripple reduction in a direct-drive outer-rotor surface-mounted permanent-magnet synchronous machine. The effects of the magnet pole arc width on the torque ripple characteristics of the machine are first established by both analytical and 2-D finite element approaches. Furthermore, the effectiveness of the axial pole pairing technique in mitigating the machine cogging torque, back electromotive force harmonics, and overall torque quality is comprehensively examined. Finally, 3-D finite element analysis and experiments are carried out to validate the proposed approach, and the results show that axial pole pairing can be cost efficiently implemented in terms of magnet material usage and assembly.

Permanent-Magnet Flux-Switching Integrated Starter Generator With Different Rotor Configurations for Cogging Torque and Torque Ripple Mitigations

This paper investigates the cogging torque and torque ripple features of a permanent-magnet flux-switching integrated starter generator. The effects of the rotor pole arc width on the cogging torque, torque ripple, and output torque are first established using finite-element analysis (FEA). Three torque ripple reduction techniques based on the optimization of three different rotor pole configurations, namely, uniform, step skewed, and axial pairing, are then proposed. The torque characteristics of each rotor configuration at varying load currents and phase angles are studied in detail. A prototype machine with a common stator and the three optimized rotor configurations are built for experimental validation. Both the FEA results and the experimental tests show that the step skewed and axial pairing techniques can alleviate the cogging torque significantly, but the latter is less effective than the former in reducing the overall torque ripple.

Six auroral generators: A review

[1] The paper reviews generator processes and configurations of six types of auroral arcs: embedded arcs, Alfvenic arcs, onset arcs, poleward arcs during substorms, auroral streamers, and auroral spirals. The arcs and generators are elements in global current systems, which are classified as Types I and II after Bostrom. The arcs may be dominated by transient processes or be quasi-stationary. The main emphasis of the paper is on the generator forces. They are pressure gradient forces, magnetic normal or shear stresses, or inertial forces. For three cases, the arcs embedded in the oval convection, the poleward arc during substorms, and the auroral streamers, simple expressions are presented of the currents injected into the ionosphere by the generator process, allowing quantitative evaluations. The relations leading from these currents to other key auroral quantities are summarized. The apparent conflict between the widths of Alfvenic arcs and the transverse scales required for energy coupling to the topside ionospheric plasma is solved by assuming current and field filamentation by multiple reflections in the ionospheric Alfven resonator. The substorm generator is described as a high-beta plasma layer arising from collapse of the tail current sheet. An essential element in this process is the shedding of excess flux tube entropy through energy dumping in the auroral acceleration process and ionospheric dissipation. The dynamics of this process needs further investigation. The physics of the connection between flow bursts in the tail plasma sheet and the flows associated with auroral streamers in the ionosphere is discussed. Regular auroral spirals and the westward traveling surge have in common a concentration of upward field-aligned current which demands strongly enhanced dissipation. They differ by the processes creating the upward current concentration.

Methods to evaluate arc stability in plasma arc cutting torches

Plasma cutting is commonly used to cut metals in a variety of applications. This research is motivated by the lack of fundamental understanding of the dynamics of the plasma flow interacting with cold gas environment. It is focused on the characterization of the arc instabilities that affect the quality and consistency of a cut. The characterization of instabilities has been performed with high-speed Schlieren imaging technology to visualize the arc width and the light intensity fluctuations in the arc boundary layer. Measurements of arc symmetry using Fourier and wavelet transforms of the light intensity fluctuations in individual pixels in the Schlieren images are able to provide a quantitative measure for the degree of instability. Ambient gas entrainment into the plasma jet is measured using a CCD camera with a narrow bandpass filter centred on the nitrogen atomic line to detect nitrogen concentrations throughout the arc, thus showing the penetration of shield and ambient gas into the pure oxygen plasma. The effects of torch design features on these characteristics are investigated by comparing two different torch designs. The results show that the developed diagnostics are useful for evaluating new torch designs.

Magnetic Circuit & Torque Analysis of Brushless DC Motor

This work is concerned with magnetic and torque analysis of BLDCM and with development of a method of designing BLDCM that have symmetric winding on the rotor .make significant contribution to the rotor inductance position difficult. It is also show that the prediction detent torque can be extremely sensitive to the permanent magnet by altering magnet arc width. Finally, simple lumped models that allow one to predict motor performance and characteristics as a function of main dimension, magnet residual flux density and phase current are developed. These models are used as a basis for an approach to designing BLDCM.

Coordinated control and experimentation of the dental arch generator of the tooth‐arrangement robot

The traditional way of acquiring the dental arch curve form is based on manual operation, which will randomly bring numerous errors caused by human factors. The purpose of this paper is to automatically acquire the dental arch curve and implement the coordinated control of the dental arch generator of the multi-manipulator tooth-arrangement robot, which can be used in full denture manufacturing. Based on the arc length constant theory, kinematics on dental arch generator is analyzed. The control pulse realization methods of high-resolution timing and CPU time-stamp timing are studied, and testing and comparative analysis of the control precision and stability of the two methods is carried out. Control experimentation of the dental arch generator and preliminary tooth-arrangement experimentation are performed using the multi-manipulator tooth-arrangement robot system. The dental arch generator can automatically generate a dental arch curve that fits a patient according to the patient's jaw arch parameters. Repeated positioning accuracy is 0.12 mm for the slipways which drive the dental arch generator. The maximum value of single point error is 1.64 mm when the arc width direction (x-axis) is 37.25 mm. The experimental results indicate that the method of control pulse realized by high-resolution timing to achieve high precision coordinated motion control of dental arch generator of tooth-arrangement robot is feasible. The error analysis results indicate that the control strategy and technical route can fulfill the requirements for motion speed and location precision. A novel system to generate the tooth arch curve has been developed. The traditional method of manually determining the dental arch may soon become obsolete in favour of the use of a robot to assist in generating a more standard tooth arch curve. The system can be used to manufacture a full denture. It will lay an important theoretical foundation for quantitative research of oral restoration, and also provide a way to standardize the manufacturing process of full denture.

Observations of the auroral width spectrum at kilometre-scale size

Abstract. This study examines auroral colour camera data from the Canadian Dense Array Imaging SYstem (DAISY). The Dense Array consists of three imagers with different narrow (compared to all-sky view) field-of-view optics. The main scientific motivation arises from an earlier study by Knudsen et al. (2001) who used All-Sky Imager (ASI) combined with even earlier TV camera observations (Maggs and Davis, 1968) to suggest that there is a gap in the distribution of auroral arc widths at around 1 km. With DAISY observations we are able to show that the gap is an instrument artifact and due to limited spatial resolution and coverage of commonly used instrumentation, namely ASIs and TV cameras. If the auroral scale size spectrum is indeed continuous, the mechanisms forming these structures should be able to produce all of the different scale sizes. So far, such a single process has not been proposed in the literature and very few models are designed to interact with each other even though the range of their favourable conditions do overlap. All scale-sizes should be considered in the future studies of auroral forms and electron acceleration regions, both in observational and theoretical approaches.

General Analytical Models of Inductance Matrices of Four-Pole Bearingless Motors With Two-Pole Controlling Windings

In this paper, after introducing the bearingless motor's working principle in brief, we analyze the magnetic field distribution principle of the bearingless motor. We then derive in detail the general analytical models of inductance matrices of a four-pole bearingless motor with two-pole controlling windings. The derived general analytical models are applicable not only to bearingless motors with a salient-pole rotor, but also to bearingless motors with a cylindrical rotor. By setting different values of salient-pole arc width parameter rho in the general models of inductance, the analytical models of inductance of different types of bearingless motors, such as bearingless induction motors, bearingless synchronous reluctance motors, and bearingless surface-mounted permanent magnet (SPM) motors, can be derived.

Cycle-Life Characterization of Automotive Lithium-Ion Batteries with LiNiO2 Cathode

A set of lithium-ion cells containing a -based positive electrode and a graphite negative electrode were cycled nonintrusively at high power (5C rate) and elevated temperature . The aged cells were characterized at prescribed cycle numbers (up to 5250 cycles) by a three-electrode cell, capacity measurement, and electrochemical impedance spectroscopy (EIS). Excellent cyclability of these cells under typical hybrid-electric vehicle conditions is demonstrated by 18% capacity fade after 5250 cycles, and the discharge capacity shows a mainly parabolic behavior with the cycle number (dependent on ) in the initial stage and a linear behavior (dependent on ) for subsequent cycles. Using a lithium reference electrode further reveals that the capacity fade during cycling is primarily caused by the positive electrode, where discharge capacity may be limited by a decrease in active lithium intercalation sites in the oxide particles. The increase in full-cell impedance with cycling is evident from the increase in midfrequency arc width , composed of charge-transfer kinetic resistance and transport resistance through the solid electrolyte interphase (SEI), . More specifically, the cell-impedance rise comes mainly from the rising and of the positive electrode. Based on individual electrode EIS spectra and equivalent-circuit analysis, it is found that the rise in the positive electrode is far more influential than the change in . Therefore, property modification and thickening of the SEI layer of the positive electrode during cycling appear to be dominant factors in cell-impedance rise and power fade.

Statistical study of inverted-V structures in FAST data

Abstract. Since the 1970s the inverted-V structures have been observed in the satellite-borne particle data. These Λ-shaped enhancements of the differential energy flux on the high energy channels on the top of low number flux on the lower energies are traces of auroral particle acceleration by U-shaped potential drops along the field lines within the auroral zones. In this study, we show the results of a statistical study of inverted-V events in five years (1997–2001) of the Fast Auroral SnapshoT (FAST) electron spectrograms. We found 588 well-defined events in total, but the statistical results are also shown for a subset of 97 very best events. The statistical analysis shows that the inverted-V's mainly occur within the auroral oval latitudes (65°–75° invariant latitude), in the pre-midnight sector (21–23 magnetic local time) and during the Northern Hemisphere winter months (November to February). The typical maximum energies of the inverted-V's are 2–4 keV, when a threshold value of 0.3 keV is used as a selection criterion. This corresponds to an acceleration potential drop of a few kV. The typical peak energy tends to increase towards the magnetic midnight. Most of the inverted-V events occur during magnetically quiet or moderate activity, Kp 1–4. The usual width of an inverted-V varies from 20 to 40 km and is comparable to the peak value of the typical meso-scale auroral arc width of 10–20 km. Furthermore, the polar cap potential values estimated from the SuperDARN radar data are always at least three times larger than the inverted-V acceleration potential drop.

Mandibular canine index as a sex determinant: A study on the population of western Uttar Pradesh

Objective: To establish the effectiveness of mandibular canine index in predicting sex in Western Uttar Pradesh population. Materials and Methods: 200 subjects belonging to Western Uttar Pradesh population (100 males; 100 females) in the age group of 17-25 yrs were included. Impressions were made with alginate and study models prepared with dental stone. Maximum mesiodistal diameter of mandibular canines and the linear distance between tips of mandibular canines were measured using a Vernier caliper. Observed mandibular canine index (MCIo) was calculated as the ratio between the maximum mesiodistal width of mandibular canine and canine arc width. Results: Left canine exhibited greater sexual dimorphism i.e. 9.05% as compared with right canine i.e. 8.782%. Sex could be predicted correctly in approximately 70% of subjects examined. Conclusion: With the standard MCI it was possible to detect sex in the population of Western Uttar Pradesh to an extent of about 72%. Hence it is considered as a quick, easy and reproducible method for determining the sex of an individual.

WE‐C‐224C‐06: Influence of Air Gap On Dosimetric Characteristics of Uniform and Composite Clinical 90Y Plaques for Dural Irradiation

Purpose: A semi‐cylindrical polycarbonate plaque incorporating a 90Y foil has been developed and used to irradiate the dura in 14 spinal tumor patients. It has been hypothesized that inadequate fitting of the irradiator plaque to the dural surface could adversely affect the area of therapeutic dose delivery at the 90% level. A differentially‐loaded composite treatment plaque has been designed to ameliorate potential air gap effects and maximize therapeutic dose delivery. Method and Materials: Two clinical plaque designs were evaluated, including a “standard” plaque containing a single foil of uniform activity, and a “composite” plaque containing a differentially‐loaded 90Y source created by placing a single activated square foil under an activated foil frame of the same outer dimensions in a titanium shell. Two dosimetry phantoms surrounded by a layer of radiochromic film (GafChromic HS) were constructed with radii approximating a perfect fit (matched to inner plaque radius) and a gap fit (80% of inner plaque radius) and irradiated with the two plaques. Results: Analysis of the irradiated film demonstrated that the effective treatment width to 90% of the plaque along the arc in the standard plaque is 65.8% when fitted and 58.1% in the presence of a gap; for the composite plaque, the corresponding treatment widths to 90% are 88.6% when fitted and 69.4% in the presence of a gap. Thus, in the presence of a gap the composite plaque delivers dose at the 90% level to a 19.6% greater arc width than the standard plaque with a gap, and 5.5% greater arc width than a perfectly fitted standard plaque. Conclusion: Differentially‐loaded composite 90Y plaques deliver therapeutic dose to a substantially larger treatment area than standard plaques currently used, and completely resolve treatment area to the 90% level potentially lost to inadequate fit with standard plaques.

Torque ripple reduction in exterior-rotor permanent magnet synchronous motor

The paper presents torque ripple reduction in permanent magnet synchronous motor with exterior-rotor. The influence of the magnet pole arc width and the influence of the supply current waveform on the torque ripple are considered in the analysis. The results of the analysis are obtained by the finite element method simulation and are verified experimentally as well. The reduction of total torque ripple at nominal load conditions less than 2% is achieved by proper motor magnet pole arc design and by applying the optimal stator current waveform control.

Descriptive patterns of severe chronic pulmonary hypertension by chest radiography

To find chest roentgenographic (CXR) features to help differentiate two representative diseases with severe chronic pulmonary hypertension (PH). Thirty-six consecutive patients with chronic thromboembolic PH (CTEPH), 38 with primary PH (PPH), and 37 with left heart disease and PH. CXRs were reviewed about 6 features (left 2nd arc protrusion, right descending pulmonary artery diameter (rPAD), cardiothoracic ratio (CTR), right 2nd arc width, avascular area and pleural abnormality). Hemodynamic data and the degree of tricuspid regurgitation (TR) on echocardiography were compared with CXR findings. The diagnostic pattern of CTEPH was the presence of one of two findings, an avascular area or marked rPAD (>20mm) together with pleuritic change. The diagnostic pattern of PPH was one of the two features; without pleuritic abnormality, marked left 2nd arc protrusion (>10mm) or moderate left 2nd arc protrusion (5-10mm) with marked rPAD (<20mm). The sensitivity for the diagnosis of CTEPH among the three diseases was 78% and specificity was 92%. The sensitivity for the diagnosis of PPH was 45% and specificity was 88%. CTR and right 2nd arc width were related to the degree of TR in CTEPH and PPH. Characteristic roentgenographic findings can help differentiate two frequent diseases associated with chronic pulmonary hypertension and reflect the severity of disease.

Pro-kinetic medications as aids in imaging the small bowel by video-capsule

The m2a wireless video-capsule (Given Imaging Ltd., Israel) is a miniature ingestible camera utilized for the color imaging of the small intestine walls. Despite its diagnostic yield superiority over all other diagnostic modalities, a substantial part of the pathologies are not spotted. Considering the transmitted pictures high quality a resolution problem is ruled out, but rather it is assumed that parts of the intestinal wall surface are missed in the imaging process. Another important problem is the difficulty encountered by the capsule in crossing the antro-duodenal junction, probably due to pyloric hypomotility. Pro-kinetic drugs are capable of increasing the small intestine peristaltic wave velocity and contractile amplitude, thus assisting the video-capsule movements and widening the camera photo arc. The arc width is directly proportional to the surface imaging capacity. A specific dose range (cisapride 25-30 mg, metoclopramide 30 mg approximately) is calculated and an analysis is made of the use of these pro-kinetic drugs to increase the device diagnostic yield. It should be emphasized that: (1) despite a potential risk for complications, such as bleeding from small intestine lesions, radiological studies underline the high safety profile of metoclopramide; (2) increased capsule speed of progress is not expected to cause a loss of imaged area; (3) an oral dose below 15 mg (metoclopramide or cisapride) may not suffice to accelerate the capsule transit through the antro-duodenal junction. The concept is patent protected.

Model of auroral electron acceleration by dissipative nonlinear inertial Alfvén wave

In a recent work [Wu, 2003a, 2003b], a dissipative nonlinear inertial Alfvén wave (DNIAW) were proposed as the physical explanation for the formation of the strong electric spikes often observed in the auroral ionosphere and the magnetosphere. DNIAW can also lead to the field_aligned electron acceleration. In the present paper, dynamical characteristics of DNIAW acceleration are discussed and its possible role in auroral electron acceleration is further investigated. The effective acceleration region for auroral electrons with energies of the order of keV produced by DNIAW acceleration is between 0.5 and 2.5 RE above the ionosphere, and the most efficient acceleration occurs around 0.8 RE where both the Alfvén velocity and the produced auroral electron energy peak, and the peak energy is around 10 keV. We suggest that this could explain the precipitous decrease of the auroral electron energy spectrum toward energies above 10 keV, which can be inferred from measurements of energy distribution of precipitating auroral electrons. Typical widths of auroral arcs caused by the DNIAW acceleration are in scales of the order of 1 km.

Percutaneous humeroplasty of posterolateral humeral head defects (Hill-Sachs) associated with anterior shoulder dislocation: a cadaveric study (SS-63)

The significance of the Hill-Sachs lesion in relation to recurrent anterior dislocations of the shoulder has been well described. While numerous procedures have been devised for the treatment of recurrent anterior shoulder dislocations associated with these defects, none are directly aimed at correcting the lesion itself. A percutaneous bone tamp has been used successfully in treating central tibial articular depressions seen in plateau fractures. We propose that the percutaneous bone tamp can be used to correct or decrease the size of large Hill-Sachs defects which we will term “humeroplasty.” The purpose of our study was to evaluate whether percutaneous humeroplasty can be used to achieve correction of a large Hill-Sachs defect. Our hypothesis is that percutaneous humeroplasty can reduce large Hill-Sachs lesions to normal. Fourteen cadaveric humeri were used for our study. The average age was 49.9 years. There were 13 males, 1 female. A reproducible, “significant” Hill-Sachs defect that was morphologically similar to in vivo lesions was created, as defined by previous studies. Defect arc depth, arc width and the length were then measured and will be used to calculate the volumetric loss from the Hill-Sachs lesion as well as volume restoration following humeroplasty. The defect was then reduced visually and under fluoroscopic guidance using our percutaneous humeroplasty technique. This technique involves a 10-mm diameter cortical window created in the mid-greater tuberosity just lateral to the bicipital groove, through which the curved bone tamp is directed to the defect and correction is obtained. The residual defect following humeroplasty was then measured and recorded. Paired t tests were used to compare the pre- to post-humeroplasty parameters including arc depth, width, length, and volume as well as comparing post-humeroplasty measurements to no defect. Significance is set at P = .05. The average arc depth, width, length, and volume of the Hill-Sachs defect measured 8.9 mm, 16.3 mm, 24.1 mm, and 1755.6 mm3, respectively. Following percutaneous humeroplasty, these defects were reduced to 1.6 mm, 6.2 mm, 10.4 mm, and 50.3 mm3, respectively. All reductions were statistically significant (P < .001). When the reduced defect arc depth, width, length, and volume were compared with no defect (0 mm or 0 mm3), there was a statistically significant difference in all parameters (P < .001). We were able to reproducibly create large Hill-Sachs deformities in vitro. While we were not able to prove our hypothesis that percutaneous humeroplasty can reduce large Hill-Sachs lesions to normal, we were able to significantly reduce these to “small” defects, as described in previous clinical studies. This reduction of the Hill-Sachs lesion to a “small” defect may prevent the increased risk of recurrence normally seen following the surgical treatment of anterior shoulder instability with large Hill-Sachs defects. Additional cadaveric research followed by clinical studies is needed to further investigate percutaneous humeroplasty as a viable technique for the treatment of anterior shoulder instability with large Hill-Sachs lesions.

Optical signatures of auroral arcs produced by field line resonances: comparison with satellite observations and modeling

Abstract. We show two examples from the CANOPUS array of the optical signatures of auroral arcs produced by field line resonances on the night of 31 January 1997. The first example occurs during local evening at about 18:00 MLT (Magnetic Local Time), where CANOPUS meridian scanning photometer data show all the classic features of field line resonances. There are two, near-monochromatic resonances (at approximately 2.0 and 2.5 mHz) and both show latitudinal peaks in amplitude with an approximately 180 degree latitudinal phase shift across the maximum. The second field line resonance event occurs closer to local midnight, between approximately 22:00 and 22:40 MLT. Magnetometer and optical data show that the field line resonance has a very low frequency, near 1.3 mHz. All-sky imager data from CANOPUS show that in this event the field line resonances produce auroral arcs with westward propagation, with arc widths of about 10 km. Electron energies are on the order of 1 keV. This event was also seen in data from the FAST satellite (Lotko et al., 1998), and we compare our observations with those of Lotko et al. (1998). A remarkable feature of this field line resonance is that the latitudinal phase shift was substantially greater than 180 degrees. In our discussion, we present a model of field line resonances which accounts for the dominant physical effects and which is in good agreement with the observations. We emphasize three points. First, the low frequency of the field line resonance in the second event is likely due to the stretched topology of the magnetotail field lines, with the field line resonance on field lines threading the earthward edge of the plasma sheet. Second, the latitudinal phase structure may indicate dispersive effects due to electron trapping or finite ion gyroradius. Third, we show that a nonlocal conductivity model can easily explain the parallel electric fields and the precipitating electron energies seen in the field line resonance.Key words. Magnetospheric physics (electric fields; energetic particles precipitating; current systems)