High-energy Shear Research Articles

One-time mass production of AlN nanosheets: Synergistic effect of high-energy shear and effective collision in a sanding mill

Aluminum nitride (AlN) has attracted huge attention in new energy vehicle, communication equipment fields, due to the high-thermal conductivity and reliable insulating ability. One of the most crucial factors is the preparation of high-performance AlN powders, and more significantly, the two-dimensional nanostructure would change the phonon vibration mode and transport process, bringing in the novel heat conduction and electricity properties. In this paper, kilogram of two-dimensional aluminum nitride nanosheets (AlNNS) with thicknesses around 30 nm and particle sizes around 400 nm were prepared by a new strategy for the nano sanding process, in which they still keep high purity (impurity content ppm grade) without further purification. Furthermore, the technological parameters of the sanding time and line speed are found as the key factors, that would affect the transformation process from hexagonal AlN into super-thin AlNNS. The morphology of the nanosheets is more complete at the line speed of 8 m/s. In addition, AlNNS have an increase of 7% in thermal conductivity (at 50 °C) compared to that of raw powders. Moreover, AlNNS have stronger sintering activity due to the larger specific surface area, in which show an increase of 16.8% in shrinkage. Therefore, AlNNS would represent excellent physical properties more than thermal conductivity, providing a new dimension research in high-thermal conductivity ceramics. Last but not least, nano sanding strategy as a purely physical process, avoids the subsequent chemical purification process, and has the advantages of simple and efficient, low energy consumption and environmental protection.

Macro-meso damage characteristics of coal body under different pressure relief conditions.

The mining of the protective coal seam usually produces different pressure relief effects on the different areas of protected coal seam, the reason is that the stress paths of protected seam coal body in different areas caused by mining effect are different. In order to explore the differential pressure relief damage effect of coal body under different pressure relief conditions, the stress evolution path of coal body in different areas of the protected coal seam is obtianed by using theoretical analysis and the macro-micro damage characteristics of coal body under different stress paths by using numerical simulation in this paper. The results show that: The damage characteristics of the sample models are basically the same in the in-situ stress recovery stage and the mining disturbance stage of the two stress paths. With ith the sequence of stress stages experienced by the sample model, the distribution of acoustic emission events concentrates in the high-intensity area and the porosity continues to decrease. The number of cracks increases slowly in the stage of in-situ stress recovery stage, most of which are tensile cracks, while the number of cracks increases sharply in the mining disturbance stage, most of which are shear cracks. The difference of the deformation and macro meso damage characteristics of the sample models under the two stress paths is mainly reflected in the post mining pressure relief stage. At the post mining pressure relief stage of path 1, the number of cracks in the sample has little growth, and most of them are small energy tensile cracks, and the porosity increases, which verifies its obvious pressure relief activation antireflection effect; At this stage of path 2, the crack growth of the sample is obvious, and most of them are high-energy shear cracks, and the porosity continues to decrease. Compared with path 1, the pressure relief expansion effect of the sample model is suppressed and the compression damage continues to develop in this stage of path 2.

Flexible freestanding MoS2-based composite paper for energy conversion and storage.

The construction of flexible electrochemical devices for energy storage and generation is of utmost importance in modern society. In this article, we report on the synthesis of flexible MoS2-based composite paper by high-energy shear force milling and simple vacuum filtration. This composite material combines high flexibility, mechanical strength and good chemical stability. Chronopotentiometric charge–discharge measurements were used to determine the capacitance of our paper material. The highest capacitance achieved was 33 mF·cm−2 at a current density of 1 mA·cm−2, demonstrating potential application in supercapacitors. We further used the material as a cathode for the hydrogen evolution reaction (HER) with an onset potential of approximately −0.2 V vs RHE. The onset potential was even lower (approximately −0.1 V vs RHE) after treatment with n-butyllithium, suggesting the introduction of new active sites. Finally, a potential use in lithium ion batteries (LIB) was examined. Our material can be used directly without any binder, additive carbon or copper current collector and delivers specific capacity of 740 mA·h·g−1 at a current density of 0.1 A·g−1. After 40 cycles at this current density the material still reached a capacity retention of 91%. Our findings show that this composite material could find application in electrochemical energy storage and generation devices where high flexibility and mechanical strength are desired.

Plough fracture of the anterior arch of the atlas: a biomechanical investigation

"Plough" fracture, in which the odontoid ploughs through and causes a high-energy shear fracture of the anterior arch of the atlas, has been documented in clinical case studies and classified as clinically unstable. Our objectives were to develop a biomechanical model to simulate atlantal plough fracture and investigate injury mechanisms. Horizontally aligned head impacts into a padded barrier were simulated using a human upper cervical spine specimen (occiput through C3) mounted to a surrogate torso mass on a sled and carrying a surrogate head. We divided 13 specimens into 3 groups based upon head-impact location: upper forehead in the midline, upper lateral side of the forehead, and upper lateral side of the head. Post-impact fluoroscopy and anatomical dissection documented the injuries. Time-history biomechanical responses were determined for neck loads, accelerations, and motions. A single specimen sustained a plough fracture variant to the atlantal anterior arch due to impact to the upper forehead and continued forward torso momentum. Horizontal velocity of C3 at the time of forehead impact was 2.7 m/s. This specimen had an anteriorly displaced fracture fragment consisting of the inferior portion of the atlantal anterior arch together with multiple complete fractures of the axis. Peak force occurred first at the impact barrier (1,903.0 N; 47 ms) followed by the neck (1,715.9 N; 58 ms). Forward translation ended at 48 ms for the head and 72 ms for the C3 vertebra. Our present results, though preliminary, indicate that plough fracture of the anterior arch of the atlas likely occurred immediately following or simultaneously with associated axis fractures at approximately 58 ms following impact to the upper forehead. The present injury response data highlighted the role of load transfer from torso momentum to the upper cervical spine to produce anterior shear force and forward displacement of the dens and bony fragment of the anterior arch of the atlas relative to the C1 ring.

Head and neck injury patterns in fatal falls: Epidemiologic and biomechanical considerations

Fatal falls often involve a head impact, which are in turn associated with a fracture of the skull or cervical spine. Prior authors have noted that the degree of inversion of the victim at the time of impact is an important predictor of the distribution of skull fractures, with skull base fractures more common than skull vault fractures in falls with a high degree of inversion. The majority of fatal fall publications have focused on skull fractures, and no research has described the association between fall circumstances and the distribution of fractures in the skull and neck. In the present study, we accessed data regarding head and neck fractures resulting from fatal falls from a Swedish autopsy database for the years 1992–2010, for the purposes of examining the relationships between skull and cervical spine fracture distribution and the circumstances of the fatal fall.Out of 102,310 medico-legal autopsies performed there were 1008 cases of falls associated with skull or cervical spine fractures. The circumstances of the falls were grouped in 3 statistically homogenous categories; falls occurring at ground level, falls from a height of <3 m or down stairs, and falls from ≥3 m. Only head and neck injuries and fractures that were associated with the fatal CNS injuries were included for study, and categorized as skull vault and skull base fractures, upper cervical injuries (C0–C1 dislocation, C1 and C2 fractures), and lower cervical fractures. Logistic regression modeling revealed increased odds of skull base and lower cervical fracture in the middle and upper fall severity groups, relative to ground level falls (lower cervical <3 m falls, OR = 2.55 [1.32, 4.92]; lower cervical ≥3 m falls, OR = 2.23 [0.98, 5.08]; skull base <3 m falls, OR = 1.82 [1.32, 2.50]; skull base ≥3 m falls, OR = 2.30 [1.55, 3.40]). C0–C1 dislocations were strongly related to fall height, with an OR of 8.3 for ≥3 m falls versus ground level. The findings of increased odds of skull base and lower cervical spine fracture in falls from a height are consistent with prior observations that the risk of such injuries is related to the degree of victim inversion at impact. The finding that C0–C1 dislocations are most common in falls from more than 3 m is unique, an indication that the injuries likely result from high energy shear forces rather than pure tension, as previously thought.

Arthroscopic Reduction and Percutaneous Pinning of a Radiocarpal Dislocation

Kamal, Robin N. MD1; Bariteau, Jason T. MD1; Beutel, Bryan G. BS2; DaSilva, Manuel F. MD1 Author Information

Arthroscopic Treatment of Radiocarpal Dislocation (SS-48)

Introduction Radiocarpal dislocations are complex injuries characterized by having a high-energy shear and rotational force to the wrist. While these injuries were previously managed using closed reduction and immobilization, recent reports have recognized the instability of these complex injuries, and have described treatment algorithms using open reduction and internal fixation. Current management of radiocarpal dislocations has been based on the following previously described principals: concentric reduction of the radiocarpal joint, identification and appropriate treatment of intercarpal ligament injuries, and stable repair of the osseous-ligamentous avulsions. Treatment with wrist arthroscopy has never been described. We report a case of ulnar radiocarpal wrist dislocation successfully treated with wrist arthroscopy and percutaneous pinning Methods A 23-year-old right-hand–dominant man presented after a motor vehicle accident with a right ulnar radiocarpal wrist dislocation, ulnar styloid fracture, and triquetrum avulsion fracture. The patient was taken to the operating room where a closed reduction was attempted. During stress exam under fluoroscopic imaging, it was apparent that a closed reduction was unobtainable, and we converted to wrist arthroscopy. From the 3-4 portal, a portion of the radioscaphocapitate ligament was seen interposed within the radiocarpal joint preventing concentric reduction of the carpus. The ligament was reflected back into position and the carpus subsequently concentrically reduced. From the 4-5 portal the dorsal radiocarpal ligament was found to be ruptured and was debrided. Two K-wires were placed across the wrist; one was placed proximal to the radial styloid through the scaphoid and capitate, and the second placed from proximal to the radial styloid through the radius, and across the lunate and triquetrum. The wrist was immobilized for 3 months, and the pins were then removed. Results At the 4-month follow-up appointment, the patient had grip strength of 86 lbs, compared to 145 lbs in his contralateral hand (59%), with 40 degrees of flexion and 60 degrees of extension. At 10 months, the patient had full pronation and supination, grip strength of 130 lbs compared to 155 lbs in the contralateral hand (84%), and lacked only 20 degrees of wrist flexion compared to the contralateral side. He returned to his pre-injury job as a manual laborer. Conclusion This is the first description of an ulnar radiocarpal dislocation successfully treated with wrist arthroscopy and percutaneous pinning. While the current applications for wrist arthroscopy are extensive, its use in fracture and dislocations of the carpus are limited. Advantages of wrist arthroscopy are that it allows for direct visualization and treatment of intercarpal and midcarpal injuries. More importantly, treatment of these injuries can be completed with minimal disruption of the soft tissues. While our treatment algorithm followed the majority of the previously described treatment principles for the treatment of radiocarpal dislocations, we did not address neurovascular structures and the extrinsic wrist ligaments, which would require open decompression. Our results show that a successful clinical outcome and stable radiocarpal wrist joint are obtainable by addressing intercarpal injuries arthroscopically, and stabilizing the radiocarpal joint.

Efficacy of Removal of Sucrose-Supplemented Interproximal Plaque by Electric Toothbrushes in an In Vitro Model

Electric toothbrushes were evaluated using a model of plaque removal by fluid shear forces. Sucrose supplementation during plaque development did not affect the removal of bacteria from biofilm exposed to low-energy shear but did increase their resistance to high-energy shear. The toothbrush supplying high-energy shear forces removed significantly more viable bacteria.

Radio Emission from Three-dimensional Relativistic Hydrodynamic Jets: Observational Evidence of Jet Stratification.

We present the first radio emission simulations from high-resolution three-dimensional relativistic hydrodynamic jets; these simulations allow us to study the observational implications of the interaction between the jet and the external medium. This interaction gives rise to a stratification of the jet in which a fast spine is surrounded by a slow high-energy shear layer. The stratification (in particular, the large specific internal energy and slow flow in the shear layer) largely determines the emission from the jet. If the magnetic field in the shear layer becomes helical (e.g., resulting from an initial toroidal field and an aligned field component generated by shear), the emission shows a cross section asymmetry, in which either the top or the bottom of the jet dominates the emission. This, as well as limb or spine brightening, is a function of the viewing angle and flow velocity, and the top/bottom jet emission predominance can be reversed if the jet changes direction with respect to the observer or if it presents a change in velocity. The asymmetry is more prominent in the polarized flux because of field cancellation (or amplification) along the line of sight. Recent observations of jet cross section emission asymmetries in the blazar 1055+018 can be explained by assuming the existence of a shear layer with a helical magnetic field.