scholarly journals Dissipation of Impact Stress Waves within the Artificial Blasting Damage Zone in the Surrounding Rocks of Deep Roadway

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Jianguo Ning ◽  
Jun Wang ◽  
Yunliang Tan ◽  
Xinshuai Shi
Keyword(s):  
Damage Zone ◽  
Normal Incidence ◽  
Field Application ◽  
Stress Waves ◽  
Vibration Energy ◽  
Elastic Zone ◽  
Impact Stress ◽  
Intact Rock Mass ◽  
The Impact ◽  
Inside Out

Artificial explosions are commonly used to prevent rockburst in deep roadways. However, the dissipation of the impact stress wave within the artificial blasting damage zone (ABDZ) of the rocks surrounding a deep roadway has not yet been clarified. The surrounding rocks were divided into the elastic zone, blasting damage zone, plastic zone, and anchorage zone in this research. Meanwhile, the ABDZ was divided into the pulverizing area, fractured area, and cracked area from the inside out. Besides, the model of the normal incidence of the impact stress waves in the ABDZ was established; the attenuation coefficient of the amplitude of the impact stress waves was obtained after it passed through the intact rock mass, and ABDZ, to the anchorage zone. In addition, a numerical simulation was used to study the dynamic response of the vertical stress and impact-induced vibration energy in the surrounding rocks. By doing so, the dissipation of the impact stress waves within the ABDZ of the surrounding rocks was revealed. As demonstrated in the field application, the establishment of the ABDZ in the surrounding rocks reduced the effect of the impact-induced vibration energy on the anchorage support system of the roadway.

THE REDUCTION OF STRESS WAVE PROPAGATION THROUGH POROUS MATERIALS

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1215-1220
Author(s):  
SOTO AKI KIDA ◽  
KEITA FUKUSHIMA ◽  
MASAYA MATSUMOTO
Keyword(s):  
Porous Medium ◽  
Porous Materials ◽  
Stress Wave ◽  
Acrylic Resin ◽  
Wave Theory ◽  
Stress Waves ◽  
Stress Wave Propagation ◽  
Impact Stress ◽  
The Impact ◽  
Impact Stress Wave

Impact stress wave propagating through porous materials is investigated in order to examine the ability of the shock absorbing effect. The specimens are modeled as the porous medium with different porous diameters made of the acrylic resin plate. When these models are impacted with different impact velocities, the impact stress waves propagating before and after the porous parts are measured using the strain gages in the experiments. As the reduction effect of the impact stress wave propagating in the porous medium, we pay attention to the maximum stresses and the duration times from the histories of the impact stress waves. One-dimensional wave theory and dynamic element method simulated this model are applied in order to explain these phenomena.

scholarly journals Rapid Assessment of Tree Damage Resulting from a 2020 Windstorm in Iowa, USA

Forests ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 555
Author(s):  
Thomas C. Goff ◽  
Mark D. Nelson ◽  
Greg C. Liknes ◽  
Tivon E. Feeley ◽  
Scott A. Pugh ◽  
...  
Keyword(s):  
Forest Inventory ◽  
Damage Zone ◽  
Satellite Image ◽  
Rapid Assessment ◽  
Aerial Survey ◽  
Inventory Data ◽  
Tree Damage ◽  
Forest Inventory Data ◽  
Damage Susceptibility ◽  
The Impact

A need to quantify the impact of a particular wind disturbance on forest resources may require rapid yet reliable estimates of damage. We present an approach for combining pre-disturbance forest inventory data with post-disturbance aerial survey data to produce design-based estimates of affected forest area and number and volume of trees damaged or killed. The approach borrows strength from an indirect estimator to adjust estimates from a direct estimator when post-disturbance remeasurement data are unavailable. We demonstrate this approach with an example application from a recent windstorm, known as the 2020 Midwest Derecho, which struck Iowa, USA, and adjacent states on 10–11 August 2020, delivering catastrophic damage to structures, crops, and trees. We estimate that 2.67 million trees and 1.67 million m3 of sound bole volume were damaged or killed on 23 thousand ha of Iowa forest land affected by the 2020 derecho. Damage rates for volume were slightly higher than for number of trees, and damage on live trees due to stem breakage was more prevalent than branch breakage, both likely due to higher damage probability in the dominant canopy of larger trees. The absence of post-storm observations in the damage zone limited direct estimation of storm impacts. Further analysis of forest inventory data will improve understanding of tree damage susceptibility under varying levels of storm severity. We recommend approaches for improving estimates, including increasing spatial or temporal extents of reference data used for indirect estimation, and incorporating ancillary satellite image-based products.

scholarly journals Increased Construct Stiffness With Meniscal Repair Sutures and Devices Increases the Risk of Cheese-Wiring During Biomechanical Load-to-Failure Testing

2021 ◽  
Vol 9 (6) ◽  
pp. 232596712110156
Author(s):  
Sebastian Müller ◽  
Tanja Schwenk ◽  
Michael de Wild ◽  
Dimitris Dimitriou ◽  
Claudio Rosso
Keyword(s):  
Characteristic Curve ◽  
Meniscal Repair ◽  
Suture Fixation ◽  
Contributing Factors ◽  
Mode Of Failure ◽  
Load To Failure ◽  
Pull Through ◽  
Optimal Stiffness ◽  
The Impact ◽  
Inside Out

Background: Cheese-wiring, the suture that cuts through the meniscus, is a well-known issue in meniscal repair. So far, contributing factors are neither fully understood nor sufficiently studied. Hypothesis/Purpose: To investigate whether the construct stiffness of repair sutures and devices correlates with suture cut-through (cheese-wiring) during load-to-failure testing. Study Design: Controlled laboratory study. Methods: In 131 porcine menisci, longitudinal bucket-handle tears were repaired using either inside-out sutures (n = 66; No. 0 Ultrabraid, 2-0 Orthocord, 2-0 FiberWire, and 2-0 Ethibond) or all-inside devices (n = 65; FastFix360, Omnispan, and Meniscal Cinch). After cyclic loading, load-to-failure testing was performed. The mode of failure and construct stiffness were recorded. A receiver operating characteristic curve analysis was performed to define the optimal stiffness threshold for predicting meniscal repair failure by cheese-wiring. The 2-tailed t test and analysis of variance were used to test significance. Results: Loss of suture fixation was the most common mode of failure in all specimens (58%), except for the Omnispan, which failed most commonly because of anchor pull-through. The Omnispan demonstrated the highest construct stiffness (30.8 ± 3.5 N/mm), whereas the Meniscal Cinch (18.0 ± 8.8 N/mm) and Ethibond (19.4 ± 7.8 N/mm) demonstrated the lowest construct stiffness. The Omnispan showed significantly higher stiffness compared with the Meniscal Cinch ( P < .001) and Ethibond ( P = .02), whereas the stiffness of the Meniscal Cinch was significantly lower compared with that of the FiberWire ( P = .01), Ultrabraid ( P = .04), and FastFix360 ( P = .03). While meniscal repair with a high construct stiffness more often failed by cheese-wiring, meniscal repair with a lower stiffness failed by loss of suture fixation, knot slippage, or anchor pull-through. Meniscal repair with a stiffness >26.5 N/mm had a 3.6 times higher risk of failure due to cheese-wiring during load-to-failure testing (95% CI, 1.4-8.2; P < .0001). Conclusion: Meniscal repair using inside-out sutures and all-inside devices with a higher construct stiffness (>26.5 N/mm) was more likely to fail through suture cut-through (cheese-wiring) than that with a lower stiffness (≤26.5 N/mm). Clinical Relevance: This is the first study investigating the impact of construct stiffness on meniscal repair failure by suture cut-through (cheese-wiring).

Research on Automatic Detection Technology for Coal Seam Floor Failure Features

2011 ◽  
Vol 467-469 ◽  
pp. 1870-1875 ◽  
Author(s):  
Guang Ming Zhao ◽  
Xiang Rui Meng
Keyword(s):  
Coal Seam ◽  
Water Inrush ◽  
Damage Zone ◽  
Detection Technology ◽  
Floor Failure ◽  
Industry Practice ◽  
Iteration Model ◽  
Forward Calculation ◽  
Mining Coal ◽  
The Impact

By the impact of coal mining, coal floor will produce distortion and damage, and make the damage zone which may result in water inrush from the floor of coal seam. CT technology with DC electricity is used to analyze two-dimensional point source current field by employing the forward calculation, inverse iteration, model correction and other methods. On the basis, inverted resistivity image of the detecting zone is obtained, which can help to determine damage law and damage depth of coal seam floor. And then the possibility of water inrush from the coal floor is analyzed. Industry practice shows that the research results are credible and can play an important guiding role in the controlling of water inrush.

Advances in Chinese research on Azolla

1985 ◽  
Vol 86 ◽  
pp. 161-167 ◽  
Author(s):  
Thomas A. Lumpkin
Keyword(s):  
Green Manure ◽  
Field Application ◽  
Symbiotic Relationship ◽  
Aquatic Fern ◽  
Communication Problems ◽  
The Impact

SynopsisThe aquatic fern Azolla has a symbiotic relationship with an N2-fixing cyanobacterium. Fanners in China and Vietnam have used Azolla for centuries as a green manure for rice and as fodder for pigs, ducks and fish. Chinese researchers have been studying Azolla since the early 1950's but many of their achievements are unknown outside China because of language and other communication problems. This article reviews current Chinese Azolla research and focuses on the impact of newly introduced Azolla species in the areas of field application, use of spores, and isolation of the N2-fixing symbiont.

Rails Deformation Pattern in Frontal Impact

2002 ◽  
Author(s):  
Joseph Hassan ◽  
Guy Nusholtz ◽  
Ke Ding
Keyword(s):  
Wave Propagation ◽  
Real World ◽  
Stress Waves ◽  
Stress Wave Propagation ◽  
Deformation Pattern ◽  
Frontal Impact ◽  
Rigid Barrier ◽  
Final Deformation ◽  
Deformation Patterns ◽  
The Impact

During a vehicle crash stress waves can be generated at the impact point and propagate through the vehicle structure. The generation of these waves is dependent, in general, on the crash type and, in particular, on the impact contact characteristics. This has consequences with respect to different crash barrier interfaces for vehicle evaluation. The two barriers most commonly used to evaluate the response of a vehicle in a frontal impact are the rigid barrier and the offset deformable barrier. They constitute different crash modes, full frontal and offset. Consequently it would be expected that there are different deformation patterns between the two. However, an additional possible contributor to the difference is that an impact into a rigid barrier generates waves of significantly greater stress than impacts with the deformable one. If stress waves are a significant component of real world final deformation patterns then, the choice of barrier interface and its effective stiffness is critical. To evaluate this conjecture, models of two types of rails each undergoing two different types of impacts, are analyzed using an explicit dynamic finite element code. Results show that the energy perturbation along the rail depends on the barrier type and that the early phase of wave propagation has very little effect on the final deformation pattern. This implies that in the real world conditions, the stress wave propagation along the rail has very little effect on the final deformed shape of the rail.

scholarly journals Ability of near-infrared spectroscopy and chemometrics to predict the age of mosquitoes reared under different conditions

2020 ◽  
Author(s):  
Oselyne Ong ◽  
Elise Kho ◽  
Pedro Esperança ◽  
Chris Freebairn ◽  
Floyd Dowell ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
Near Infrared Spectroscopy ◽  
Near Infrared ◽  
Field Application ◽  
Machine Learning Techniques ◽  
Island Population ◽  
Natural Environments ◽  
Pls Regression ◽  
Field Methods ◽  
The Impact

Abstract Background: Practical, field-ready age-grading tools for mosquito vectors of disease are urgently needed because of the impact that daily survival has on vectorial capacity. Previous studies have shown that near-infrared spectroscopy (NIRS), in combination with chemometrics and predictive modeling, can forecast the age of laboratory-reared mosquitoes with moderate to high accuracy. It remains unclear whether the technique has utility for identifying shifts in the age structure of wild-caught mosquitoes. Here we investigate whether models derived from the laboratory strain of mosquitoes can be used to predict the age of mosquitoes grown from pupae collected in the field. Methods: NIR spectra from adult female Aedes albopictus mosquitoes reared in the laboratory (2, 5, 8, 12 and 15 days old) were compared to spectra from mosquitoes emerging from wild-caught pupae (1, 7 and 14 days old). Different partial least squares (PLS) regression methods trained on spectra from laboratory mosquitoes were evaluated on their ability to predict the age of mosquitoes from more natural environments. Results: Models trained on spectra from laboratory-reared material were able to predict the age of other laboratory-reared mosquitoes with moderate accuracy and successfully differentiated all day 2 and 15 mosquitoes. Models derived with laboratory mosquitoes could not differentiate between field-derived age groups, with age predictions relatively indistinguishable for day 1-14. Pre-processing of spectral data and improving the PLS regression framework to avoid overfitting can increase accuracy, but predictions of mosquitoes reared in different environments remained poor. Principle component analysis confirms substantial spectral variations between laboratory and field-derived mosquitoes despite both originating from the same island population. Conclusions: Models trained on laboratory mosquitoes were able to predict ages of laboratory mosquitoes with good sensitivity and specificity though they were unable to predict age of field-derived mosquitoes. This study suggests that laboratory-reared mosquitoes do not capture enough environmental variation to accurately predict the age of the same species reared under different conditions. Further research is needed to explore alternative pre-processing methods and machine learning techniques, and to understand factors that affect absorbance in mosquitoes before field application using NIRS.

scholarly journals The Impact Stress of PC Piles in the Soft Ariake Clay Bed

1981 ◽  
Vol 21 (2) ◽  
pp. 151-160
Author(s):  
Yûshirô Iwao ◽  
Masami Hiwatashi
Keyword(s):  
Impact Stress ◽  
The Impact

Dynamic Stress-Strain Relations for Annealed 2S Aluminum Under Compression Impact

1953 ◽  
Vol 20 (4) ◽  
pp. 523-529
Author(s):  
J. E. Johnson ◽  
D. S. Wood ◽  
D. S. Clark
Keyword(s):  
Dynamic Stress ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Impact Stress ◽  
Stress Strain Relation ◽  
Final Strain ◽  
Dynamic Relations ◽  
Single Stress ◽  
The Impact

Abstract This paper presents the results of an experimental study of the stress-strain relation of annealed 2S aluminum when subjected to compression impact. Two methods of securing a dynamic stress-strain curve are considered, namely, from the measurement of impact stress as a function of maximum plastic strain, and impact stress as a function of the impact velocity. The dynamic stress-strain curves obtained by these methods lie considerably above the static curve. The elevation in stress of the dynamic relations above the static relation increases progressively from zero at the elastic limit to about 20 per cent at a strain of 4.5 per cent. However, the two dynamic relations are not coincident which indicates that the behavior of the material cannot be described by a single stress-strain curve for all impact velocities. A family of stress-strain curves which differ slightly from each other and which depend upon the final strain is postulated in order to correlate both sets of data adequately.

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