Multiple Arcs Research Articles

Reduced basis method for the elastic scattering by multiple shape-parametric open arcs in two dimensions

We consider the elastic scattering problem by multiple disjoint arcs or cracks in two spatial dimensions. A key aspect of our approach lies in the parametric description of each arc's shape, which is controlled by a potentially high-dimensional, possibly countably infinite, set of parameters. We are interested in the efficient approximation of the parameter-to-solution map employing model order reduction techniques, specifically the reduced basis method. Initially, we utilize boundary potentials to transform the boundary value problem, originally posed in an unbounded domain, into a system of boundary integral equations set on the parametrically defined open arcs. Our aim is to construct a rapid surrogate for solving this problem. To achieve this, we adopt the two-phase paradigm of the reduced basis method. In the offline phase, we compute solutions for this problem under the assumption of complete decoupling among arcs for various shapes. Leveraging these high-fidelity solutions and Proper Orthogonal Decomposition (POD), we construct a reduced-order basis tailored to the single arc problem. Subsequently, in the online phase, when computing solutions for the multiple arc problem with a new parametric input, we utilize the aforementioned basis for each individual arc. To expedite the offline phase, we employ a modified version of the Empirical Interpolation Method (EIM) to compute a precise and cost-effective affine representation of the interaction terms between arcs. Finally, we present a series of numerical experiments demonstrating the advantages of our proposed method in terms of both accuracy and computational efficiency.

Research on Digital Construction Technology for Special-Shaped Shell Pipe Structures

The aesthetic appeal of special-shaped shell pipe structures makes them highly favored by architects and holds promising prospects for various applications. In the detailed design stage, NURBS curves should be divided into multiple continuous arcs due to the limitations of current steel structure fabrication equipment, which can only accommodate pipes with equal-curvature bends. However, the traditional manual fitting methods suffer from several issues including low efficiency, undercutting at the interface, poor smoothness of curves, and lack of control over tolerances. Furthermore, the weaker out-of-plane stiffness and utilization of bending arc pipe sections pose significant challenges in terms of spatial positioning and installation accuracy that need to be addressed. The study focuses on addressing these challenges by investigating digital construction technology for special-shaped shell pipe structures and developing a parametric algorithm that enables automatic fitting of spatial NURBS curves into multiple arcs, thereby achieving seamless curve fitting. A post-processing program was developed to enable the parametric generation of fabrication and installation information for structural members, which can be seamlessly integrated into the BIM database. Finally, structural position control technology is proposed to improve assembly efficiency and ensure consistency between the completed construction state and the design shape. The above digital construction technology has been applied in projects such as the Haihua Island International Conference Center. It can provide complete technical solutions for modeling of special-shaped shell pipe structures, including establishment of a member information database, fabrication at the workshop and installation on site, construction organization management, as well as installation accuracy control.

The Digital Superhero: Conspiracy and Convergence

ABSTRACT The superhero is a popular figure in contemporary media: not just single characters, plots and movies, but entire universes and ‘phases’ spread across multiple protagonists, narrative arcs, devices, mediums and formats, from films and television shows to video games and books. Across much content, a reliance on conspiracy is evident: to motivate characters, link together plots, and move them across time and space. This article articulates paranoia and conspiracy as an emergent aesthetic bound up with the affordances of digital technology. It thus articulates these aesthetic impulses as the outcome of a cultural logic of convergence embodied in the affordances and demands of digital technologies and ecosystems. Considering the three aspects of convergence culture identified by Henry Jenkins (technology, culture, participation), and how they operate within superhero media under the aegis of digitization, this article discusses their penumbra: conspiratorial technology, conspiratorial culture, and conspiratorial participation.

Elastic Fields Around Multiple Stiff Prestressed Arcs Located on a Circle

Abstract The plane strain problem of an isotropic elastic matrix subjected to uniform far-field load and containing multiple stiff prestressed arcs located on the same circle is considered. The boundary conditions for the arcs are described by those of either Gurtin–Murdoch or Steigmann–Ogden theories in which the arcs are endowed with their own elastic energies. The material parameters for each arc can in general be different. The problem is reduced to the system of real variables hypersingular boundary integral equations in terms of two scalar unknowns expressed via the components of the stress tensors of the arcs. The unknowns are approximated by the series of trigonometric functions that are multiplied by the square root weight functions to allow for automatic incorporation of the tip conditions. The coefficients in series are found from the system of linear algebraic equations that are solved using the collocation method. The expressions for the stress intensity factors are derived and numerical examples are presented to illustrate the influence of governing dimensionless parameters.

Multi-Beam Surveying Ocean Exploration Model and Applications

With the development of artificial intelligence, fiber Bragg grating (FBG) sensing technology has garnered increasing attention. This paper first proposes a surface reconstruction algorithm based on curvature information, which is applicable to two different sensor structures: implanted FBG sensors and whisker array sensors. The design and analysis of these sensors are based on a pure bending model, where the corresponding bending curvature is obtained by measuring the wavelength shift of the fiber Bragg grating at the measurement points. Next, the paper elaborates on the surface reconstruction algorithm for the implanted FBG sensor. This sensor contains FBG sensing points that are evenly distributed. Curvature information corresponding to the position can be obtained based on the direction and magnitude of the wavelength shift. The fiber bending is considered as a connection of multiple arc segments, and the coordinates of the sensing points are calculated in the Cartesian coordinate system using the properties of the tangents. The fiber bending curve is then reconstructed by connecting the arc segments in MATLAB. Finally, the paper provides a detailed introduction to the surface reconstruction algorithm for the whisker array sensor. When the whiskers bend, the FBGs fixed on them act as curvature sensors. The curvature is determined by the FBG wavelength shift, and the three-dimensional coordinates of the whisker tip relative to the base are calculated based on a geometric model. MATLAB is then used to connect the whisker tip coordinates, completing the construction of the surface.

Study on the self-vibration characteristics of non-circular arches with cracks based on the transfer matrix method

As the span of reinforced concrete arch bridges continues to increase, so does the difficulty of construction. The structure is at risk of cracking. Most of the bridges under construction are non-circular arches, and there are few studies on such arches. The current study tried to investigate the self-vibration characteristics of non-circular arches with existing cracks. A computational approach proposed in the original non-circular arch is substituted with multiple infinitesimal arch segments having different radii of curvature, enabling the determination of natural frequencies and mode shapes of the non-circular arches with cracks. Furthermore, a finite element model (FEM) of the reinforced concrete structure with existing cracks is developed to assess the effects of various factors, including axial location, crack depth, and positions within the same cross-section. The results demonstrate the feasibility of the computational method using multiple infinitesimal arc segments with varied radii of curvature, yielding a maximum error of only 1.58 %, which satisfies engineering application standards. An increase in crack depth leads to a reduction in the natural frequencies of specific modes of the structure, while the effect on others is insignificant. For cracks situated at the top or bottom plates within the same cross-section, the impact differs based on the local deformation being convex or concave. If the deformation is convex, the top plate cracks exhibit a higher rate of change in natural frequencies compared to the bottom plate cracks; conversely, with concave deformation, the bottom plate cracks have a greater influence than the top plate cracks.

Stereotactic Radiation Therapy in 3 Fractions for T1 Glottic Cancer

To report the results of a phase I-II study on SBRT for early glottic cancer. This a prospective study at a single Institution enrolling patients with T1 glottic cancer. The true vocal cords (TVC) were divided into thirds and the third(s) containing disease prescribed 36 Gy in 3 fractions. The portions of the TVCs next to the involved one were planned to receive 30 Gy in 3 fxs. SBRT was delivered by a LINAC-based approach using multiple arcs. Toxicity was scored by CTCAE and late events were considered those occurring 3 months after SBRT. Voice quality was investigated by the voice handicap index (VHI) at regular intervals. The planned sample size was 75 patients. Accrual was discontinued after 33 patients due to concerns for late toxicity. T stage was as follows: T1a: 23 pts (69.7%); T1b: 10 pts (30.3%). All patients received the planned treatment and the median follow-up time is 51.5 months (IQR: 47.9-61.0 months). At last follow up, all patients are alive and without evidence of disease but two patients who died for intercurrent causes. The local control rate is 100% at 4 yrs. Six patients (18.2%) developed soft tissue necrosis (N=4) or cartilage necrosis (N=2) after a median time of 14.9 months from SBRT. Five out of 6 necrotic events were observed in patients who kept smoking and/or had a recent COVID infection. All 4 soft tissue events healed with conservative therapy. After an initial deterioration the average VHI score significantly improved at 6 months over baseline. SBRT to 36 Gy in 3 fractions is highly effective in controlling T1 TVC carcinoma, but necrosis, though mostly transient, is a concern. Based on the present results, a reduction in total dose as well as a more accurate patient selection are warranted.

Tectonic Anatomy Reveals the Chinese Altai‐Kuerti‐Dulate Arc Amalgamation in the Southern Altaids

AbstractThe Erqis tectonic belt, situated at the junction of the Chinese Altai‐East Junggar, originated through the subduction of the Ob‐Zaisan Ocean, playing a pivotal role in unraveling the tectonic evolution of the southern Altaids. Tectonic and provenance analyses discern three distinct arcs: the Chinese Altai in the north exhibits a protracted history from the late Cambrian to early Permian with a slender accretionary complex (AC) termed the Supute AC; the Kuerti intra‐oceanic arc in the middle emerged during the Silurian to Devonian coevally with a minor AC known as the Tesibahan AC; and the Dulate arc in the south predominantly evolved from the Middle Devonian to Permian, giving rise to the Fuyun AC that independently developed on its northern margin at least until ∼273 Ma. Our findings indicate the existence of multiple arcs within the Ob‐Zaisan Ocean, forming an archipelago paleogeography in the Paleo‐Asian Ocean. Provenance studies lead us to propose that cryptic sutures demarcating the Chinese Altai, Kuerti, and Dulate lie approximately along the Kuerti and Tesibahan faults, respectively, and that the oceanic branches between these arcs subducted northward beneath the Chinese Altai and Kuerti arcs and southward beneath the Dulate arc. Additionally, our work demonstrates the closure of the Ob‐Zaisan Ocean most probably postdates ∼273 Ma. Combining our data with previous research, we present a novel tectonic evolution model, elucidating several arc amalgamations with multiple subduction polarities between Chinese Altai and East Junggar throughout the late Cambrian to Permian.

Ideal quadratic nodal point in half-Heusler semimetal LaPtBi

The research focus on topological states in electronic systems has recently expanded from traditional linear dispersions to encompass higher-order dispersions. These higher-order dispersions exhibit unique physical properties, including high topological charge, exotic magnetoresponse, and novel transport behaviors. In this study, we employ first-principles calculations to propose the half-Heusler material LaPtBi as an ideal quadratic nodal point semimetal. Our comprehensive analysis of the band structure reveals an ideal nodal point located precisely at the Fermi level, exhibiting quadratic dispersion in all directions. This finding is supported by symmetry analysis and effective model arguments. Moreover, when the spin-orbit coupling effect is considered, the nodal point transitions from triple to quadruple degeneracy, while maintaining its quadratic dispersion. The material also features multiple prominent arc surface states originating from the nodal point, which are distinctly separated from the bulk bands. This separation facilitates experimental verification. Overall, LaPtBi, with its quadratic nodal point and advantageous properties, serves as an ideal platform for further research. The study of this material is expected to enhance our understanding of higher-order topological states in electronic systems, potentially driving future advancements in the field.

Paleozoic subduction of the Paleo-Asian Ocean plate: Constraints from Ordovician-Carboniferous volcano-sedimentary rocks in the northern Beishan orogenic collage, NW China

The subduction history of the Hongshishan Ocean within the Beishan orogenic collage is crucial to understand the evolutionary mechanism of the Paleo-Asian Ocean. In this study, we describe the petrography, ages and geochemistry of an Ordovician–Carboniferous volcano-sedimentary succession, which provides a record of the subduction history of the Hongshishan Ocean. We obtained early Ordovician zircon U-Pb ages (482 ± 6 Ma and 472 ± 2 Ma) from the Xianshuihu Formation. The youngest weighted mean detrital zircon age from the Yuanbaoshan Formation is 421.0 ± 8.8 Ma. Most detrital zircons have prominent age peaks at 900–840 Ma and 543–462 Ma, suggesting a main source from the southern Mongolian microcontinent. Volcanic rocks from the Baishan Formation yielded weighted mean ages of 299.3–300.3 Ma. During the Ordovician–Devonian, some volcanic arcs formed on the northern side of Hongshishan-Baiheshan-Erlegen Ula (HBEU) ophiolitic belt, indicating that the Hongshishan Ocean had a northward subduction polarity. During the Carboniferous, continental arcs were well developed on both sides of the HBEU belt, suggesting a bidirectional subduction. An archipelago of multiple arcs of the Hongshishan Ocean resembles that of the West Pacific Ocean. The change in subduction polarity can be attributed to characteristics of multi-oceanic accretion.

Drone Arc Routing Problems and Metaheuristic Solution Approach

The drone arc routing problem (DARP) is one of the arc routing problems (ARPs) that has been studied by researchers recently. Unlike traditional ARPs, drones can travel directly between any two points in the graph. Due to the flexibility of drones, it is possible to use edges not defined in the graphs when deadheading the edges. This advantage of drones makes this problem more challenging than any other ARP. With this study, the energy capacities of drones are considered in a DARP. Thus, a novel DARP called the drone arc routing problem with deadheading demand (DARP-DD) is addressed in this study. Drone capacities are used both when servicing the edges and when deadheading the edges in the DARP-DD. A special case of the DARP-DD, called the multiple service drone arc routing problem with deadheading demand (MS-DARP-DD), is also discussed, where some critical required edges may need to be served more than once. To solve these challenging problems, a simulated annealing algorithm is used, and the components of the algorithm are designed. Additionally, novel neighbor search operators are developed in this study. The computational results show that the proposed algorithm and its components are effective and useful in solving the DARP-DD and MS-DARP-DD.

Diaphragm Tracking System That Superimposes Planned Diaphragm Contours on Kilovolt Cine Images During Multiple Breath-Hold Volumetric Modulated Arc Therapy for Abdominal Tumors.

We recently published a phantom validation of our diaphragm tracking system, DiaTrak, on an Elekta linear accelerator with an integrated cone-beam computed tomography (CBCT) unit for multiple breath-hold volumetric modulated arc therapy of abdominal tumors, where the diaphragm position was compared between digitally reconstructed radiography (DRR) and kilovolt (kV) projection streaming images by template matching. In the present report, the visual feedback of the diaphragm position was added to the reported system. DICOM-RT diaphragm contour data were additionally exported from a treatment planning system to the DiaTrak PC. Following phantom localization by registering the CBCT to the planning CT images, a projected diaphragm contour was overlaid on each DRR image, whereas another two projected diaphragm contours were superimposed on each kV projection cine image every 180 ms after shifting ±5 mm (set as breath-hold tolerance) in the craniocaudal direction during gantry rotation. It was visually confirmed that the projected diaphragm surface was observed within the two contour lines on the kV cine window. The diaphragm registration errors of the localized phantom were also calculated based on image cross-correlation between the DRR and the projection cine images every 180 ms. It was found that the mean diaphragm registration error was -0.29 mm with a standard deviation of 0.32 mm during the gantry rotation. In conclusion, a new interface for the 5 mm tolerance check was proposed to provide direct visual feedback, thereby giving a sense of assurance to the attending radiotherapy technologists. The calculated diaphragm registration errors were relatively small compared to the tolerance of 5 mm, and therefore it is considered clinically acceptable.

Late Paleozoic intra-oceanic arc and its accretionary complex in East Junggar (NW China): implications for multiple arc amalgamation in the southern Altaids

The East Junggar is a key to understanding the accretionary history of the southern Altaids. However, the tectonic setting and amalgamation history of the East Junggar during the Carboniferous–Permian remain controversial. Here we report new field, geochronological and geochemical data for the Carboniferous–Permian volcanic and sedimentary rocks from the Jiangjun unit and the Hongliugou ophiolitic complex of East Junggar to constrain its tectonic evolution. Carboniferous volcanic rocks, with zircon and apatite U–Pb ages from 337 ± 2 to 303 ± 32 Ma, display arc-related geochemical characteristics. Carboniferous–Permian sedimentary rocks predominantly contain Carboniferous–Permian detrital zircons and have maximum depositional ages from 318 ± 5 to 281 ± 6 Ma. Provenance analysis indicates that the sediments from the west Jiangjun unit were sourced from the Yemaquan arc and those from the east Jiangjun unit may be sourced solely from a new intra-oceanic arc. Integrated data indicate that Carboniferous–Permian strata in the Jiangjun unit were formed in the intra-oceanic arc setting that remained until the middle Permian. These analyses suggest an amalgamation process of multiple convergence and accretion for the southern Altaids during the formation of NE Pangaea in the late Paleozoic.

Quantification of Dosimetry Improvement With or Without Patient Surface Guidance

PurposeNon-coplanar beams and arcs are routinely used to improve dosimetry for intracranial cases but their application for extra-cranial cases has been hampered by the risk of collision. This has led to conservative beam selection whose impact on plan dosimetry has not been previously studied. Methods and materialA full-body 3D patient surface was acquired using optical cameras for a single lung patient at the time of CT simulation. Eight SBRT plans were created for the patient, with varying degrees of non-coplanarity and deliverability. The plans included VMAT and IMRT plans ranging from simple, coplanar arcs to multiple non-coplanar arcs and IMRT beams. There was a total of 70 fields created across the 8 plans, of which 21 fields were undeliverable with a 5cm buffer. OAR metrics including R50, Dmax 2 cm from the PTV, lung V20 and chest wall V30 were evaluated. Five expert SBRT dosimetrists from five institutions evaluated field deliverability, with or without the guidance of the clearance map. ResultsIn the dosimetry evaluation, a clear trend in increasing dosimetric compactness and OAR sparing is observed with increasing plan non-coplanarity. R50, Dmax 2cm, lung V20, and chest wall V30 decreased 41%, 39%, 43%, 57%, respectively, from plan 1 (two coplanar partial arcs) to plan 8 (19 non-coplanar IMRT beams). In the observer tests, the expert dosimetrists’ ability to accurately discern beam deliverability due to collision significantly increases with the clearance map. The errors in predicting colliding fields were eliminated using the whole-body surface and clearance map, and the user was able to select fields based on plan quality and patient comfort instead of being overly conservative. ConclusionThe study shows that incorporating a personalized, whole-body clearance map in the treatment planning workflow can facilitate the adoption of non-coplanar beams or arcs that benefit the SBRT plan dosimetry.

Characteristic study of valveless pump with dual outlet composite drainage structures

Abstract Valveless pumps are gaining importance in various fields. However, the reflux phenomenon can reduce pump performance and limit its application. This article proposes a dual outlet composite drainage structure valve-less piezoelectric pump with multiple semicircular arc structures within the flow channel to address this issue. The operating methods are explained, and the pump output flow rate formulation has been derived. The ANSYS CFX was used to simulate flow conditions in various directions. A prototype pump was then produced and tested using 3D printing technology. The results show that the flow rate gets a maximum state of 189.6 mL/min under a voltage of 200 V and a frequency of 50 Hz.

Design and Analysis of Permanent Magnet Machines With Multiple Arc Pole Ratios in Stator Teeth

Design and Analysis of Permanent Magnet Machines With Multiple Arc Pole Ratios in Stator Teeth

Application of generalized aurora computed tomography to the EISCAT_3D project

Abstract. EISCAT_3D is a project to build a multi-site phased-array incoherent scatter radar system in northern Fenno-Scandinavia. We demonstrate via numerical simulation how useful monochromatic images taken by a multi-point imager network are for auroral research in the EISCAT_3D project. We apply the generalized aurora computed tomography (G-ACT) method to modelled observational data from real instruments, such as the Auroral Large Imaging System (ALIS) and the EISCAT_3D radar. G-ACT is a method for reconstructing the three-dimensional (3D) distribution of auroral emissions and ionospheric electron density (corresponding to the horizontal two-dimensional (2D) distribution of energy spectra of precipitating electrons) from multi-instrument data. It is assumed that the EISCAT_3D radar scans an area of 0.8° in geographic latitude and 3° in longitude at an altitude of 130 km with 10 × 10 beams from the radar core site at Skibotn (69.35° N, 20.37° E). Two neighboring discrete arcs are assumed to appear in the observation region of the EISCAT_3D radar. The reconstruction results from G-ACT are compared with those from the normal ACT as well as the ionospheric electron density from the radar. It is found that G-ACT can interpolate the ionospheric electron density at a much higher spatial resolution than that observed by the EISCAT_3D radar. Furthermore, the multiple arcs reconstructed by G-ACT are more precise than those by ACT. In particular, underestimation of the ionospheric electron density and precipitating electrons' energy fluxes inside the arcs is significantly improved by G-ACT including the EISCAT_3D data. Even when the ACT reconstruction is difficult due to the unsuitable locations of the imager sites relative to the discrete arcs and/or a small number of available images, G-ACT allows us to obtain better reconstruction results.

Geochronology and Geochemistry of Granitic Pegmatites from Tashidaban Li Deposit in the Central Altun Tagh, Northwest China

The Central Altun orogenic system is a result of the amalgamation of multiple micro-continental blocks and island arcs. This complex system originated from subduction–accretion–collision processes in the Proto-Tethys Ocean during the Early Paleozoic. Research has reported the discovery of several Li-Be granitic pegmatite deposits in the Central Altun Block, including the North Tugeman granitic pegmatite Li-Be deposit, Tugeman granitic pegmatite Be deposit, Tashisayi granitic pegmatite Li deposit, South Washixia granitic pegmatite Li deposit, and Tamuqie granitic pegmatite Li deposit. The Tashidaban granitic pegmatite Li deposit has been newly discovered along the northern margin of the Central Altun Block. Field and geochemical studies of the Tashidaban granitic pegmatite Li deposit indicate: (1) Spodumene pegmatites and elbaite pegmatites, as Li-bearing granitic pegmatites that form the Tashidaban granitic pegmatite Li deposit, intrude into the two-mica schist, and marble of the Muzisayi Formation of the Tashidaban Group. (2) Columbite–tantalite group minerals and zircon U-Pb dating results indicate that the mineralization age of Tashidaban Li granitic pegmatites is 450.2 ± 2.4 Ma with a superimposed magmatic event at around 418–422 Ma later. (3) Whole-rock geochemical results indicate that the Kumudaban rock sequence belongs to the S-type high-K to calc-alkaline granites and the Tashidaban Li granitic pegmatites originated from the extreme differentiation by fractional crystallization of the Kumdaban granite pluton.

Mesoscale Auroral Curls in Antarctica

AbstractThe morphology and motion of auroras have been widely studied due to their indications on magnetospheric processes. Here, we report a new kind of “auroral curls,” which have wavelengths in the mesoscale (∼100 km) and propagate azimuthally. Utilizing data from the Chinese Antarctic Zhongshan Station (the all‐sky imager and the high‐frequency radar), the Active Magnetosphere and Planetary Electrodynamics Response Experiment and the Defense Meteorological Satellite Program, we analyze an event occurred on 23 April 2019. We find these curls are fine structures in the poleward boundary of multiple arcs. Corresponding field‐aligned currents manifest as a series of longitudinally arranged pairs, while ionospheric flow velocities nearby oscillate with periods in the Pc 5 band. Observational evidence suggests these curls are connected with ultra‐low frequency (ULF) waves, which opens the possibility of using auroras to globally image ULF waves.

Latitudinal Profiles of Auroral Forms/Motions and Plasma Properties Based on Simultaneous Image‐Particle Measurements by Reimei in the Midnight Auroral Oval

AbstractWe present the simultaneous and conjugated auroral emission and particle data obtained by a low‐altitude polar‐orbiting micro‐satellite, Reimei, for elucidating their latitudinal distributions and variations in the nightside auroral oval. Here are reported a few notable examples of the Reimei observations with high time and spatial resolutions, namely ∼120 msec. and ∼1.2 km × 1.2 km for multispectral auroral images and 40 msec. for energy‐pitch angle distributions of electrons and ions with energies of 10 eV–12 keV, respectively. The auroral images show various fine‐scale auroral activities characterized by the following types of auroral forms and variations: faint bands, streaming multiple arcs, shearing arcs, and vortices/curls, which are typical of the latitudinal properties of auroras. The particle analyzer simultaneously observed various properties of electron energy‐pitch angle and latitudinal distributions, and their temporal variations, each of which corresponds to a type of the auroral activities. Their features are summarized below. Reimei repetitively observed inverted‐V signatures of low‐energy (<1 keV) field‐aligned electrons in addition to the higher‐energy (several keV) diffuse electrons in low‐latitude auroral oval. In more active regions at higher latitudes, the dominant energy flux responsible for the multiple‐arc emissions was carried by the well‐known inverted‐V electron precipitation. The rapidly rotating vortices or so‐called curls of fine‐scale discrete auroras near the poleward boundary of the auroral oval were closely associated with the significant energy fluxes of spiky field‐aligned electron bursts with energy‐time dispersions produced by dispersive Alfvén waves.