426 research outputs found
Optimization of Plasma Plume Characteristics Based on Multi-anode Coaxial Ablative Pulsed Plasma Thruster
A special surface discharge is proposed based on the multi-anode electrode
geometry. Instead of the traditional surface flashover of creepage on the
insulator surface between the electrodes, a surface discharge with one of the
electrodes being placed far away from the insulator is achieved in this paper.
The unique electric field distribution due to the multi-anode electrode
geometry has a significant influence on the discharge process of the surface
discharge. It changes the generation and propagation process of the plasma,
forming a plasma plume contributes to the propulsion performance of the
thruster. Through theoretical analysis of the obtained plume data, it is
indicated that the ablative pulsed plasma thruster based on multi-anode
electrode geometry (short for multi-anode APPT) promotes the internal pressure
of the plasma jet during its propagation and significantly increases the
density and energy of charged particles. The discharge phenomena manifest that
the multi-anode APPT and the helix-coil multi-anode APPT effectively increase
the intensity of the plasma plume. Through electron density spatial
distribution measurement, it has been found that the helix-coil multi-anode
APPT increases the density of plasma in the axial direction to more than 4
times of the conventional coaxial APPT and reduces the electron density in
other directions. In the propulsion test, it has been demonstrated that the
multi-anode APPT and the helix-coil multi-anode APPT have better performance in
terms of the impulse bit and the thrust-to-power ratio. In addition, it is also
identified that the pinch effect will be enhanced with the increase of
discharge power and the propulsion performance is promoted more distinctly. The
multi-anode APPT and the helixcoil multi-anode APPT have been proved to have
potential application advantage in the field of micro-satellite propulsion.Comment: 12 pages, 12 figure
A Novel Text Classification Method Using Comprehensive Feature Weight
Currently, since the categorical distribution of short text corpus is not balanced, it is difficult to obtain accurate classification results for long text classification. To solve this problem, this paper proposes a novel method of short text classification using comprehensive feature weights. This method takes into account the situation of the samples in the positive and negative categories, as well as the category correlation of words, so as to improve the existing feature weight calculation method and obtain a new method of calculating the comprehensive feature weight. The experimental result shows that the proposed method is significantly higher than other feature-weight methods in the micro and macro average value, which shows that this method can greatly improve the accuracy and recall rate of short text classification
Raymond Carver’s Narrative Poetics: An Analysis of the Narrative Functions of “Key” and “Cat” in Neighbors
In Raymond Carver’s Neighbors, why does Bill, the protagonist, always have a sudden high sexual desire? What’s the use of frequent and large numbers of cats, keys and other objects? So far, almost all the relevant discussions have ignored the narrative function of “object” in the novel. In fact, the “object” as an “actor” radiates its mysterious and powerful power all the time, arouses a series of illusions and desires of the characters, affects their thoughts and actions, and finally highlights their “ontology” because of the sudden disappearance of the object, smashes the dream of the protagonists, and causes the characters and readers to think deeply about the relationship between people, objects and real life
A novel explicit design method for complex thin-walled structures based on embedded solid moving morphable components
In this article, a novel explicit approach for designing complex thin-walled
structures based on the Moving Morphable Component (MMC) method is proposed,
which provides a unified framework to systematically address various design
issues, including topology optimization, reinforced-rib layout optimization,
and sandwich structure design problems. The complexity of thin-walled
structures mainly comes from flexible geometries and the variation of
thickness. On the one hand, the geometric complexity of thin-walled structures
leads to the difficulty in automatically describing material distribution
(e.g., reinforced ribs). On the other hand, thin-walled structures with
different thicknesses require various hypotheses (e.g., Kirchhoff-Love shell
theory and Reissner-Mindlin shell theory) to ensure the precision of structural
responses. Whereas for cases that do not fit the shell hypothesis, the
precision loss of response solutions is nonnegligible in the optimization
process since the accumulation of errors will cause entirely different designs.
Hence, the current article proposes a novel embedded solid component to tackle
these challenges. The geometric constraints that make the components fit to the
curved thin-walled structure are whereby satisfied. Compared with traditional
strategies, the proposed method is free from the limit of shell assumptions of
structural analysis and can achieve optimized designs with clear load
transmission paths at the cost of few design variables and degrees of freedom
for finite element analysis (FEA). Finally, we apply the proposed method to
several representative examples to demonstrate its effectiveness, efficiency,
versatility, and potential to handle complex industrial structures
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