scholarly journals An artificial impact on the asteroid (162173) Ryugu formed a crater in the gravity-dominated regime

Science ◽  
2020 ◽  
Vol 368 (6486) ◽  
pp. 67-71 ◽  
Author(s):  
M. Arakawa ◽  
T. Saiki ◽  
K. Wada ◽  
K. Ogawa ◽  
T. Kadono ◽  
...  
Keyword(s):  
Outer Edge ◽  
Surface Strength ◽  
Impact Experiment ◽  
Small Asteroid ◽  
The Impact ◽  
Rubble Pile

The Hayabusa2 spacecraft investigated the small asteroid Ryugu, which has a rubble-pile structure. We describe an impact experiment on Ryugu using Hayabusa2’s Small Carry-on Impactor. The impact produced an artificial crater with a diameter >10 meters, which has a semicircular shape, an elevated rim, and a central pit. Images of the impact and resulting ejecta were recorded by the Deployable CAMera 3 for >8 minutes, showing the growth of an ejecta curtain (the outer edge of the ejecta) and deposition of ejecta onto the surface. The ejecta curtain was asymmetric and heterogeneous and it never fully detached from the surface. The crater formed in the gravity-dominated regime; in other words, crater growth was limited by gravity not surface strength. We discuss implications for Ryugu’s surface age.

The Performance Analysis of Calcium Silicate Composited Wall's Impact Resistance

2013 ◽  
Vol 671-674 ◽  
pp. 596-601
Author(s):  
Ming Ming Chen ◽  
Zhong Tao ◽  
Hen Min Zhang ◽  
Wen Zheng Yu
Keyword(s):  
Performance Analysis ◽  
Calcium Silicate ◽  
Impact Resistance ◽  
Engineering Application ◽  
National Standard ◽  
Minimum Standard ◽  
Impact Experiment ◽  
Interior Walls ◽  
The Impact

This paper introduces the impact experiment and an engineering application of the new composited wall which composed of calcium silicate composited board. Clearly defines the impact resistance of the wall in different connection as interior walls and exterior walls through observing the wall’s changes in the number of 5 times or even up to 50 times impact (10 times of the national standard). It can be known from the experiment that long wall has large vibration but good integrity. The window wall may fracture easily and is not able to meet the minimum standard requirements of impact resistance when the width is small. It needs to take reinforce measures.

scholarly journals Application of Mixed Linear Models in the Analysis of Road Surface Features

2015 ◽  
Vol 54 (1) ◽  
pp. 101-109 ◽  
Author(s):  
Jurgita Židanavičiūtė ◽  
Audrius Vaitkus
Keyword(s):  
Linear Models ◽  
Road Surface ◽  
Linear Regression Models ◽  
Mixed Linear Models ◽  
Time Intervals ◽  
Surface Strength ◽  
The Road ◽  
Unequally Spaced ◽  
Units Of Analysis ◽  
The Impact

The data were collected by researchers at the Road Research Institute, in a study investigating the impact of differentfactors on road surface strength. In this statistical analysis, we apply linear mixed models (LMMs) to clustered longitudinal data, inwhich the units of analysis (points in the road) are nested within clusters (sample of four different road segments), and repeatedmeasures of road strength in these different points are collected over time with unequally spaced time intervals. The data arebalanced – each cluster has the same number of units, which are measured at the same number of time points. Because of correlateddata and different clusters in which data could be correlated, linear regression models are not appropriate here, and therefore linearmixed models are applied.

scholarly journals The Impact of Dropsonde and Extra Radiosonde Observations during NAWDEX in Autumn 2016

2020 ◽  
Vol 148 (2) ◽  
pp. 809-824 ◽  
Author(s):  
Matthias Schindler ◽  
Martin Weissmann ◽  
Andreas Schäfler ◽  
Gabor Radnoti
Keyword(s):  
North Atlantic ◽  
Forecast Error ◽  
The North ◽  
Impact Experiment ◽  
Beneficial Impact ◽  
Research Aircraft ◽  
Northern Atlantic ◽  
Intensive Observation ◽  
The Impact ◽  
Unique Dataset

Abstract Dropsonde observations from three research aircraft in the North Atlantic region, as well as several hundred additionally launched radiosondes over Canada and Europe, were collected during the international North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX) in autumn 2016. In addition, over 1000 dropsondes were deployed during NOAA’s Sensing Hazards with Operational Unmanned Technology (SHOUT) and Reconnaissance missions in the west Atlantic basin, supplementing the conventional observing network for several intensive observation periods. This unique dataset was assimilated within the framework of cycled data denial experiments for a 1-month period performed with the global model of the ECMWF. Results show a slightly reduced mean forecast error (1%–3%) over the northern Atlantic and Europe by assimilating these additional observations, with the most prominent error reductions being linked to Tropical Storm Karl, Cyclones Matthew and Nicole, and their subsequent interaction with the midlatitude waveguide. The evaluation of Forecast Sensitivity to Observation Impact (FSOI) indicates that the largest impact is due to dropsondes near tropical storms and cyclones, followed by dropsondes over the northern Atlantic and additional Canadian radiosondes. Additional radiosondes over Europe showed a comparatively small beneficial impact.

Energy absorption from composite reinforced with high performance auxetic textile structure

2020 ◽  
pp. 002199832096455
Author(s):  
Fernanda Steffens ◽  
Fernando Ribeiro Oliveira ◽  
Raul Fangueiro
Keyword(s):  
Energy Absorption ◽  
High Performance ◽  
Poisson Ratio ◽  
Impact Behavior ◽  
Knitted Fabrics ◽  
Reinforced Composite ◽  
Composite Fabrication ◽  
Impact Experiment ◽  
Key Factor ◽  
The Impact

The objective of this study is to analyze the impact behavior on the basis of energy approach of weft knitted structures, namely a jersey composite and an auxetic composite using high performance yarns. Weft knitted fabrics were produced with the same structural and machine parameters, using 100% para-aramid and hybrid (47% para-aramid and 53% polyamide) structure. Composite fabrication was achieved through hand lay-up using epoxy resin. Negative Poisson ratio of the reinforcing auxetic fabric was transferred from the fabric to the composite developed. Results obtained by drop weight dart impact test show that the impact experiment with different impact loads confirmed the auxetic composites, regardless de material composition, have an increase in the total energy absorption compared to jersey reinforced composite, approximately 2.5 and 4 times more for para-aramid and hybrid composite, respectively. Auxetic composites developed within this work present great potential for applications in different areas, mainly where energy absorption is a key factor to be considered, such as in protection, sports among others.

Fracture in Taylor Rod Impact Test Specimens

2010 ◽  
Author(s):  
Sachin S. Gautam ◽  
Ravindra K. Saxena ◽  
P. M. Dixit
Keyword(s):  
Ductile Fracture ◽  
Damage Mechanics ◽  
Continuum Damage Mechanics ◽  
Outer Edge ◽  
Impact Surface ◽  
Mechanics Model ◽  
Contact Impact ◽  
Impact Problems ◽  
The Impact ◽  
Aisi1045 Steel

High velocity contact-impact problems are of great interest in industries related to aerospace, mechanical and civil engineering. Ductile fracture often occurs in such applications. Taylor rod impact tests are used as experimental and numerical tests for determining the mechanical behaviour of materials subjected to high strain rates. At sufficiently high velocities, a significant plastic deformation leading to fracture is observed. In this paper, ductile fracture in Taylor rod made of AISI1045 steel is simulated using a continuum damage mechanics model. Simulations are performed for the velocity of 250 and 300 m/s. It is observed that, at lower velocities, tensile cracks are observed at the outer edge of the impact surface. On the other hand, at higher velocities, the fracture is observed at the central axis (confined fracture) as well as at the outer edge leading to fragmentation. Both the results are consistent with the experimental results available in the literature.

Fluid Impact Under Various Tapping Conditions for Biomedical Application (Shirodhara)

2018 ◽  
Author(s):  
Swathika Meenraj ◽  
Chebolu Lakshmana Rao ◽  
Balasubramanian Venkatesh
Keyword(s):  
Integrated Circuit ◽  
Biomedical Application ◽  
Force Sensor ◽  
Intermittent Flow ◽  
Time Duration ◽  
Impact Experiment ◽  
Controlled Flow ◽  
Using Data ◽  
Short Time ◽  
The Impact

Shirodhara is an ayurveda therapy treating subjects for stress (depression/anxiety/hypertension) insomnia, headache and several kinds of psychosis. When there is a fluid impact on a solid surface, a transient impact will be developed at the interface in short time duration as vibration on forehead. The fluid impact of the liquid falling from the beaker at controlled flow rate is measured using an integrated circuit piezoelectric (ICP) force sensor for various tapping condition. The time-dependent response of the sensor is acquired using data acquisition system which is connected to the computer. The force is determined by measuring the voltage output from the piezoelectric force sensor. The impact experiment is done for single droplet, intermittent flow of drops and continuous flow of liquid falling from a fixed height of 7.5 cm. From the results, we observe the impact force for each fluid have a subtle variation depending on the falling condition and impact velocity of the fluid falling from a height.

Experimental Study on the Effect of Density of EPS Buffer Layer on the Cushioning Property of Motorcycle Helmet

2013 ◽  
Vol 455 ◽  
pp. 539-543
Author(s):  
Wei Cai Wen ◽  
Dong Ming Fu
Keyword(s):  
Experimental Study ◽  
Buffer Layer ◽  
Absorption Efficiency ◽  
Test Results ◽  
Effective Protection ◽  
Motorcycle Helmet ◽  
Energy Absorption Efficiency ◽  
Impact Experiment ◽  
The Impact ◽  
Buffer Structure

Build the model of motocross-style helmet with a dual - density and series-parallel EPS buffer layer and trial-produce helmet samples. Establish the impact experiment of the helmet model and obtain the values of HIC and Peak ACC based on the testing regulations of ECE R22.05. According to the analysis of the test results, the influence law of different EPS material densities to cushioning effect of the helmet was analyzed specifically. Experimental results show that the minimum values of HIC and Peak ACC can be obtained when the density of EPS is designed to be 0.06g/cm3; a dual - density and series - parallel EPS buffer layer has higher than 76 % of the energy absorption efficiency, and this buffer structure well reduces the values of HIC and Peak ACC, and provides effective protection for the head.

Impact Experiment and Analysis of Cantilever-Type Piezoelectric Generator

2013 ◽  
Vol 441 ◽  
pp. 594-597
Author(s):  
Xing Lin Wang ◽  
Xiao Dong Sun ◽  
Zhi Gang Yang ◽  
Yun Guang Song ◽  
Ai Juan Quan ◽  
...  
Keyword(s):  
Impact Velocity ◽  
Electric Energy ◽  
Peak Voltage ◽  
Positive Correlation ◽  
Output Waveform ◽  
Piezoelectric Generator ◽  
Impact Experiment ◽  
The Impact

An impact experiment of cantilever-type piezoelectric generator is founded in order to record and analyze the first crest of output waveform. For the first crest, the analysis results show that the impact velocity, the peak voltage and the electric energy have positive correlation. The impact velocity has little influence to electricity. With the impact amplitude raised, the peak voltage, the electricity and the electric energy will rise, however, the rate of rising will descend.

scholarly journals Impact-crater ejecta on Bennu indicate a surface with very low strength

2021 ◽  
Author(s):  
Mark Perry ◽  
Olivier Barnouin ◽  
Ronald Daly ◽  
Edward Bierhaus ◽  
Ronald-Louis Ballouz ◽  
...  
Keyword(s):  
Impact Crater ◽  
Resistance To Change ◽  
Surface Material ◽  
Escape Velocity ◽  
Surface Strength ◽  
Maximum Surface ◽  
Effective Strength ◽  
Low Strength ◽  
Initial Assembly ◽  
Rubble Pile

Abstract A planetary surface’s resistance to change is generally described as its “strength” (units of stress). The surface strength of small, rubble-pile asteroids, which consist of fragments of larger bodies that were collisionally disrupted, is poorly constrained due to their wide departure from terrestrial analogs. Here, we report the observation of an ejecta deposit surrounding an impact crater that limits the maximum surface strength of the near-Earth rubble-pile asteroid (101955) Bennu. The presence of this deposit implies that ejecta were mobilized with velocities less than the escape velocity of Bennu, 20 cm/s. Because ejecta velocities increase with surface strength, the ejecta deposit can only be explained if the effective strength of the surface material near the crater is exceedingly low, ≤100 Pa. This is three orders of magnitude below values commonly used for asteroid surfaces, but is supported by previous observations of an artificial impact crater on a similar asteroid, Ryugu. Our findings indicate a mobile surface that has likely been renewed multiple times since Bennu’s initial assembly and have far-reaching implications for interpreting observations of Bennu and other rubble piles.

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