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"Sleds"
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One-dog sleigh
A girl hitches her dog to her sleigh one morning, only to be insistently joined by a series of animals, large and small.
Book
Musher
Musher is a film about the lives of four sled dog racers (mushers) and their dogs. What it means to be a musher, and what it takes to be a sled dog, is revealed over the course of a year as they all wait out summer so they can train for the coming winter’s races. The film also explores the role of women in the sport, as dog mushing is one of just a few sports where men and women compete together.
Streaming Video
Application of the damping bag on supersonic rocket sled tests
In recent years, ground-based ultra-high-speed systems such as high-speed rocket sled and super-high-speed railways have become a research hotspot, especially the rocket sled which can currently exceed March 8 in top speed. However, due to the non-perfect smoothness of the slide and the complex aerodynamic environment, the rocket sled has a serious impact on the test articles or test instruments on the rocket sled. Therefore, it is necessary to use vibration isolation facilities to reduce the vibration on the rocket sled. In this work, a vibration damper based on the 4 damping bags with high efficiency damping effect for high-frequency vibration is design. The FEM simulation, vibration table experiments and a supersonic rocket sled test are design to demonstrate the attenuation effect of the vibration damper. All results show the vibration damper can isolate elastic waves in the frequency range from 400 Hz to 2000 Hz.
Journal Article
Features of the Application of Friction Braking in High-Speed Track Tests
The increase in the speed characteristics of newly developed aircraft models im-poses new requirements on the test bench equipment of rocket-rail tracks, including braking means. In this paper, the method of friction braking in the conditions of a rocket track is considered. A method for calculating the mode of motion of a rocket sled during friction braking and the thermal wear of the friction elements of braking devices occurring at the same time is presented. An example of the calculation of the friction braking of a conditionally specified rocket sled, per-formed according to the presented method, is shown.
Journal Article
Research on Deceleration Technology of Rocket Sled Double Track Sled
Aiming at the shortcomings of water brake in the deceleration recovery test of double-track sled, the reverse rocket deceleration was applied to the recovery of double-track sled. A deceleration scheme of rocket sled double track sled car is designed to improve the safety of double track sled car. Firstly, according to the requirements of sliding distance and water entry speed of sled, the deceleration resistance is designed and calculated, and the reverse rocket is selected. However, the sled car is designed according to the dimensions of the reverse thrust rocket, and the installation position and way of the reverse thrust rocket are determined. At last, according to the deceleration trajectory and the parameters of recoil rocket, the control mode and ignition position of recoil rocket are designed. The simulation results show that the deceleration effect of reverse rocket is obvious. This control method is simple and feasible. The reverse rocket deceleration method can be applied to the recovery of double track sled.
Journal Article
Efficient Long-Text Understanding with Short-Text Models
Transformer-based pretrained language models (LMs) are ubiquitous across natural language understanding, but cannot be applied to long sequences such as stories, scientific articles, and long documents due to their quadratic complexity. While a myriad of efficient transformer variants have been proposed, they are typically based on custom implementations that require expensive pretraining from scratch. In this work, we propose
:
iding-
ncoder and
ecoder, a simple approach for processing long sequences that re-uses and leverages battle-tested short-text pretrained LMs. Specifically, we partition the input into overlapping chunks, encode each with a short-text LM encoder and use the pretrained decoder to fuse information across chunks (
). We illustrate through controlled experiments that SLED offers a viable strategy for long text understanding and evaluate our approach on SCROLLS, a benchmark with seven datasets across a wide range of language understanding tasks. We find that SLED is competitive with specialized models that are up to 50x larger and require a dedicated and expensive pretraining step.
Journal Article
Study on finite element modeling of fiber composite external shell of rocket sled
Due to the complex mechanical environment of rocket sled test, there are some difficulties in the application of fiber composites in this field and some shortcomings in theoretical aspects such as computational simulation. This article studies the modeling of fiber composite external shells for rocket sleds. Firstly, the displacement field and constitutive relationship of the fiber composite external shell were established. A theoretical model of the rocket sled fiber external shell was established based on finite element theory. Then, according to the overload condition of the rocket sled test, the boundary conditions are applied to the model. Finally, the vibration test system is used to test the external shell test sample for model verification. The results show that the natural frequency error of the theoretical model is less than 5%, and the modal shapes exhibit a high level of consistency, which can prove the accuracy of the theoretical model established in this paper. Thus, the correctness of the proposed method was verified.
Journal Article
Dynamic response analysis of missile-sled separation in warhead rocket sled test
The warhead’s attitude upon hitting the target stands as a pivotal factor influencing its dynamic damage effect. This paper addresses the issue of interference posed by the sled and separation device on the warhead’s attack angle during endpoint effect rocket sled tests. Employing an impact dynamics analysis method, we simulate the dynamic response of the missile-sled separation process. Four models are devised, combining two types of rocket sled structures and two variations of arc rail devices with distinct parameters. Comparative analysis is conducted on the sled’s separation distance, the warhead’s attitude, and the sled’s stress. We optimize the rocket sled structure to ensure unhindered separation of the warhead and the sled, followed by verification tests. Analysis reveals that a small curvature radius and insufficient sled stiffness lead to structural failure. Consequently, the sled interferes with the warhead, impacting the target’s attack angle. To address this, we introduce a middle snap ring and slipper to reinforce the sled, along with an increased curvature radius. These two enhancement measures effectively resolve the separation interference issue between the sled and the projectile. The attack angle shift from −0.5° to 1.1° in two sled tests, thus fulfilling the experimental requirements.
Journal Article