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Guide to knife & axe throwing
Learn everything you need to know about throwing all forms of projectiles, from deceptively simple steel knives to hatchets and tomahawks. Also included is rare information on making suitable targets, selecting the correct devices, tossing from all distances and positions, as well as knife- and ax-throwing history.
Book
The principles of cascading power limits in small, fast biological and engineered systems
In biological and engineered systems, an inherent trade-off exists between the force and velocity that can be delivered by a muscle, spring, or combination of the two. However, one can amplify the maximum throwing power of an arm by storing the energy in a bow or sling shot with a latch mechanism for sudden release. Ilton et al. used modeling to explore the performance of motor-driven versus spring-latch systems in engineering and biology across size scales. They found a range of general principles that are common to animals, plants, fungi, and machines that use elastic structures to maximize kinetic energy. Science , this issue p. eaao1082 Combining motors, springs, and latches offers many routes to optimization of mechanical power in biological and engineered systems. Mechanical power limitations emerge from the physical trade-off between force and velocity. Many biological systems incorporate power-enhancing mechanisms enabling extraordinary accelerations at small sizes. We establish how power enhancement emerges through the dynamic coupling of motors, springs, and latches and reveal how each displays its own force-velocity behavior. We mathematically demonstrate a tunable performance space for spring-actuated movement that is applicable to biological and synthetic systems. Incorporating nonideal spring behavior and parameterizing latch dynamics allows the identification of critical transitions in mass and trade-offs in spring scaling, both of which offer explanations for long-observed scaling patterns in biological systems. This analysis defines the cascading challenges of power enhancement, explores their emergent effects in biological and engineered systems, and charts a pathway for higher-level analysis and synthesis of power-amplified systems.
Journal Article
Track and field takedown
When Ring Lake Middle School decides to host an Olympic Fest, Kyle is assigned to compete in the track and field throwing events--will practice make him good, or will he embarrass himself in front of everyone?
Book
Ballistic facility for heavy bodies acceleration
This paper discusses the issues of creating a ballistic facility for use in laboratory conditions and achieving throwing speeds of up to 2000 m/s for massive objects. The design of the facility was proposed and the results of the analytical calculation of the achieved speeds were presented. The verification of the analytical calculation and the results of experiments on the prototype ballistic facility was done.
Journal Article
Relationship of shoulder internal and external rotation peak force and rate of force development to throwing velocity in high school and collegiate pitchers
The purpose of this research was to characterize the difference between high school (HS) and collegiate pitcher’s throwing velocity, shoulder internal (IR) and external rotator (ER) maximum strength (Fmax) and rate of force development (RFD) and explore relationships between these measures. Competitive HS and collegiate pitchers (n = 26) participated in a single session assessment in which shoulder rotator isometric Fmax and RFD were quantified via a portable strain gauge device and throwing velocity via radar. Paired t-tests, stepwise linear regression models and correlational analyses were used to answer the questions of interest. No significant differences (p > 0.05) in pitching velocity were observed between HS and collegiate pitchers, and all pitchers were pooled into one sample for subsequent analyses. For both IR and ER models, the explained variance of Fmax with throwing velocity was small (R2 = 0.12–0.13). RFD and arm length did not contribute to the models. Large correlations (r ≥ 0.50; p < 0.001) were observed between IR and ER for Fmax and RFD measures, as well as between Fmax and RFD for IR and ER. In terms of throwing velocity, having strong IR and ER Fmax capabilities would seem more important than the ability to express force quickly in this cohort.
Journal Article
Design of a Feeding Device for Penaeus Vannamei Breeding Pond
At present, the mechanization of shrimp culture in China is still low, and most of them are artificially fed. Artificial feeding is not only labor-intensive, but also has the disadvantages of uneven feed throwing. In this paper, a feeding device for Penaeus Vannamei breeding pond is designed, which mainly includes guide trolley, support body, feeding rod, storage plate and storage bucket, the feeding efficiency of Penaeus Vannamei is improved.
Journal Article
Analysis on Rockburst Failure Energy Evolution of Model Specimen Under Stress Gradient
Rockburst is a safety problem that needs to be solved urgently in deep rock and mineral exploitation. The stress gradient is an important factor affecting rockburst. To explore the influence mechanism of stress gradient on rockburst, the loading and unloading tests of rockburst physical model under different stress gradients are carried out using the self-developed gas–liquid composite rockburst test device. Based on the strain test results of rockburst model, the spatial distribution characteristics of elastic energy are analyzed. The particle size distribution characteristics and throwing kinetic energy of debris after the rockburst of model are studied. The following conclusions are obtained: (1) the value of the stress gradient coefficient m reflected by the strain within the range of the model loading rockburst gradient 1 affects the temporal and spatial distribution of energy release process; (2) With the increase of the vertical loading stress gradient, the rockburst debris gradually changes from large plate debris to small flake, block and powder debris. The maximum ejection distance of rockburst debris gradually increases, and the dynamic failure phenomenon of rockburst becomes more and more obvious; (3) As the loading stress gradient increases, the throwing kinetic energy of rockburst debris per unit mass shows an increasing trend. The research results are of great significance to tunnel safety construction and rockburst early warning.HighlightsThe stress gradient is an important factor affecting rockburst in deep rock mass engineering.The value of the stress gradient coefficient affects the temporal and spatial distribution of energy release process.As the loading stress gradient increases, the rockburst debris gradually changes from large plate debris to small flake, block and powder debris.With the increase of the stress gradient, the maximum ejection distance of debris gradually increases, and the dynamic failure tends to be severe.
Journal Article
Superrotation charge and supertranslation hair on black holes
A
bstract
It is shown that black hole spacetimes in classical Einstein gravity are characterized by, in addition to their ADM mass
M
, momentum
P
→
, angular momentum
J
→
and boost charge
K
→
, an infinite head of supertranslation hair. The distinct black holes are distinguished by classical superrotation charges measured at infinity. Solutions with super-translation hair are diffeomorphic to the Schwarzschild spacetime, but the diffeomorphisms are part of the BMS subgroup and act nontrivially on the physical phase space. It is shown that a black hole can be supertranslated by throwing in an asymmetric shock wave. A leading-order Bondi-gauge expression is derived for the linearized horizon supertranslation charge and shown to generate, via the Dirac bracket, supertranslations on the linearized phase space of gravitational excitations of the horizon. The considerations of this paper are largely classical augmented by comments on their implications for the quantum theory.
Journal Article
Information technology assists in the innovative development of throwing embroidered balls
This study aims to understand the historical and development of throwing embroidered balls, combine information processing and drone technology to innovate throwing techniques, improve the competitive level and competition rules, promote the high-pole throwing embroidered balls to the international sports. Utilizing literature review method to clarify the evolution history of throwing embroidered balls; using mathematical statistics to analyze the results of competition during the 12th and 13th Guangxi Student Games; Using mechanics analysis and animation production methods innovate throwing techniques. The imperfect competition rules, inconsistent specifications of embroidered balls, and outdated throwing techniques have hindered the healthy development of throwing embroidery ball. The optimal throwing angle range for innovative throwing techniques is between 64° < α < 72°, with the range of throwing speed being between 13.04 m/s < v < 13.70 m/s. When α < 66°, v≈13.70m/s, the ball passes through the lower edge of the top of the circle; When α > 64°, v≈13.04m/s, when α < 72°, v≈13.17m/s, the ball passes through the upper edge of the bottom of the circle. Drone aerial photography technology can assist judges; using animation production techniques to form throwing motion models to guide training can improve competitive skills. Improving competition rules, unifying the use of competition balls, and strengthening the integration of information technology with ethnic sports can effectively enhance the development level of the sport of throwing embroidered balls.
Journal Article
Estimation of factors contributing to level differences in Japanese university decathlon athletes
This study aimed to estimate the factors that cause differences in competition level based on the competition performance structure among university student decathletes in Japan. The results of factor analysis using the maximum likelihood method (Oblimin rotation), assuming a five-factor structure estimated from parallel analysis and the information criterion, revealed the following competitive performance structures: \"running speed and body projection,” \"running endurance,” \"rotational throwing power,” \"translational throwing power,” and \"vertical leaping power.” Some of these were similar to the competitive performance structures of the world’s top athletes, but they were found to have a unique structure: two throwing powers. The analysis results using latent rank theory allowed us to evaluate them on a seven-point scale. The calculated item reference profile, difficulty index, and discrimination index for each rank indicated that shot put and 100 and 400 m performance formed the basis of decathlon performance. In addition, high jump and pole vault, which fall under the category of \"vertical leaping power,\" retained high difficulty and discrimination and were revealed to affect the stage of achievement of overall performance in the decathlon.
Journal Article