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"Catapult."
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Make a catapult
\"Discusses the science behind catapults and includes instructions for readers to build their own from household materials.\"-- Provided by publisher.
Book
Research on load release decision speed testing technology of pneumatic catapult system
The load release decision speed is a critical parameter of the pneumatic catapult system. Speed testing is of great significance for calculating load kinetic energy and evaluating the overall performance of pneumatic catapult systems. To obtain the load release decision speed during the catapult process of pneumatic catapult systems, three devices were used to conduct actual measurements: a high-speed camera, a high-precision angle encoder, and a Hall-type positioning speed sensor. The test results indicate that all three testing devices can effectively obtain the load release decision speed, and the testing method is feasible. Among the three testing schemes, the high-speed camera provides the highest speed measurement results, the angle encoder provides the lowest results, and the positioning speed sensor’s results fall between the two. The maximum relative error among the three measurements is only 0.3%, and the measurement results show good consistency.
Journal Article
I can make fantastic fliers
\"Introduces the reader on how to make flyers\"-- Provided by publisher.
Book
Low-Alkali Assisted Instant Catapult Steam Explosion Enhances Enzymatic Hydrolysis of Corn Stover by Alleviating Anti-Enzymatic Hydrolysis Factors Through Lignin Structural Rearrangement
The effective deconstruction of lignocellulosic biomass is essential for sustainable biorefineries. In this study, corn stover was pretreated by low-alkali (1–5 wt% NaOH) pre-impregnation assisted instant catapult steam explosion (ICSE) to investigate its influence on enzymatic hydrolysis efficiency and the mechanism of lignin-derived anti-enzymatic factors. The results showed that this pretreatment effectively enhanced glucose yield. Under 4–5% NaOH conditions, washed samples achieved glucose yields above 98%. At 4% NaOH, the glucose yields of washed and unwashed groups were 98.88% and 56.34%, respectively, indicating that washing removed soluble inhibitors. LC-MS analysis identified three major water-soluble inhibitory compounds-vanillin, syringaldehyde, and 2-carboxybenzaldehyde-confirming their negative effects on cellulase activity. The alkali-soluble lignin content of unwashed samples (43.28%) was 1.36 times higher than that of washed samples (31.93%), demonstrating its role as a water-insoluble inhibitory factor. Moreover, SEM, XRD, FTIR, and contact angle analyses revealed that 5% NaOH treatment enhanced lignin solubilization, induced structural rearrangement and interfacial hydrophilic reconstruction, and increased cellulose crystallinity and enzyme accessibility. These findings elucidate the mechanistic pathways of lignin transformation and inhibition mitigation, providing valuable insights for efficient and sustainable biomass conversion.
Journal Article
From the elastica compass to the elastica catapult: an essay on the mechanics of soft robot arm
An elastic rod is clamped at one end and has a dead load attached to the other (free) end. The rod is then slowly rotated using the clamp. When the load is smaller than the buckling value, the rod describes a continuous set of quasi-static forms and its end traces a (smooth, convex and simple) closed curve, which would be a circle if the rod were rigid. The closed curve is analytically determined through the integration of the Euler’s elastica, so that for sufficiently small loads the mechanical system behaves as an ‘elastica compass’. For loads higher than that of buckling, the elastica reaches a configuration from which a snap-back instability occurs, realizing a sort of ‘elastica catapult’. The whole quasi-static evolution leading to the critical configuration for snapping is calculated through the elastica and the subsequent dynamic motion simulated using two numerical procedures, one ad hoc developed and another based on a finite-element scheme. The theoretical results are then validated on a specially designed and built apparatus. An obvious application of the present model would be in the development of soft robotic limbs, but the results are also of interest for the optimization analysis in pole vaulting.
Journal Article
Safety analysis of catapult takeoff of carrier-based aircraft using System-Theoretic Process Analysis method
Catapult takeoff has become the main way for carrier-based aircraft to take off. However, as a complex process of multi-system coupling and multi-control actions link, it is an important task to ensure the safety of catapult takeoff. Therefore, this paper adopts the System-Theoretic Process Analysis (STPA) and establishes a model of catapult takeoff using the Systems Theoretic Accident Model and Process(STAMP) model. To carry out safety analysis, identify unsafe control actions and extract the causes of unsafe behavior, simulation analysis is also carried out for typical unsafe actions. The results show that using STPA to make safety analysis, combined with simulation, can comprehensively analyze and evaluate the safety of catapult takeoff, which helps identify the risk before the flight test and reduce the flight test risk.
Journal Article
THE DESIGN OF A CATAPULT MACHINE
This article will present the elements of the external structure of the catapulting machine, together with the catapulting mechanism and the operating principle of the whole assembly. In addition to these aspects, the paper will also contain notions related to materials or mechanics used. All these details combated lead to the complete definition of the analyzed product.
Journal Article
Multi-Parameter Optimization for the Wet Steam Accumulator of a Steam-Powered Catapult
Selecting the optimal parameters for wet steam accumulator of steam-powered catapult is an important task, due to launching safety. There is no literature on the topic of the parameters optimization for wet steam accumulator of steam-powered catapult. The genetic algorithm (GA) was used to determine the optimal wet steam accumulator in this article. The sink-off-the-bow (SOB), angle of attack and rate of climb were used to create the objective function. The multi-objective optimization can be converted to single-objective optimization, which is subject to angle of attack and rate of climb. Moreover, the simulation model of the steam catapult system was built by creating a thermodynamics model of steam-powered catapult, a mathematical model of traction release device, a statics model of tensioning, a statics model of full takeoff power, a mathematical model of catapult force build-up with holdback, a model of release, a dynamics model of power stroke, a dynamics model of free deck run and a dynamics model of fly away. Finally, the optimal combination of the wet steam accumulator was obtained via numerical simulation. The GA method can effectively find the optimal parameters of wet steam accumulator, and its optimized parameters can increase the safety of catapult launch process.
Journal Article
Modeling and Estimation of the Pitch Angle for a Levitating Cart in a UAV Magnetic Catapult Under Stationary Conditions
The paper presents a method for modeling and estimating the orientation of a launch cart in the magnetic suspension system of an innovative UAV catapult. The catapult consists of stationary tracks lined with neodymium magnets, generating a trough-shaped magnetic field. The cart levitates above the tracks, supported by four containers housing high-temperature YBCO superconductors cooled with liquid nitrogen. The Meissner effect, characterized by the expulsion of magnetic fields from superconductors, ensures stable hovering of the cart. The main research challenge was to determine the cart’s orientation relative to the tracks, with a focus on the pitch angle, which is critical for collision-free operation and system efficiency. A dedicated measurement stand equipped with Hall sensors and Time-of-Flight (ToF) distance sensors was developed. Hall sensors mounted on the cart’s supports captured magnetic field data at specific points. To model the tracks, the CRISP-DM (Cross Industry Standard Process for Data Mining) methodology was employed—a structured framework consisting of six stages; from problem understanding and data preparation to model evaluation and deployment. This approach guided the analysis of data-driven models and facilitated accurate pitch angle estimation. Evaluation metrics, including mean squared error (MSE), were used to identify and select the optimal models. The final model achieved an MSE of 0.084°, demonstrating its effectiveness for precise orientation control.
Journal Article
Experience with modeling values of the virtual catapult range
The development of a virtual catapult involves the synthesis of knowledge from several fields, namely physics, probability, statistics, regression analysis, and computer science. Our contribution is not focused on the description of the creation of the application from the software point of view, but it presents a method by which it is possible to generate the numerical values of the range of the virtual catapult along with their corresponding variability. When modeling these range values, it is possible to choose the classical theoretical approach, i. e., the physical approach using equations of motion, or to statistically process the measured values obtained by experimenting with a real catapult model. In our case, a statistical approach, specifically the Design of Experiments method, was chosen to estimate the values of the catapult range. The obtained appropriate regression model was used as the output of the statistical analysis of the measured data for point estimates of the range at specific settings of selected parameters of a real catapult. In order for the results of the simulated range values to correspond to the actual range values of the catapult, it was necessary to achieve a realistic fluctuation (randomness) of the results in the simulation of the catapult ranges around the predicted range value obtained from the regression model. This article suggests a way to ensure stochasticity when modeling such types of systems.
Journal Article