排序方式: 共有11条查询结果,搜索用时 31 毫秒
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The low velocity and low energy impact response of two common sheet mold compound (SMC) material systems—SMC-R27, and SMC-R37—were
investigated. In addition to characterizing the low velocity impact response and failure progression of the material systems,
the edge effects of diamond saw cutting, waterjet cutting and abrasive waterjet cutting were investigated using optical microscopy
and contact surface profilometry. Impact force–time and displacement–time responses were measured and used to characterize
energy absorption capabilities and potential correlation to post processing operation and fiber volume fraction. Pre and post-impact
edge surface micrographs were examined to relate the failure behavior on the machined surfaces. Experiments and measurements
all show that the failure zone size and growth behavior are clearly dependent on the edge finishing process. 相似文献
3.
Woon-Hong Yeo Shieng Liu Jae-Hyun Chung Yaling Liu Kyong-Hoon Lee 《Analytical and bioanalytical chemistry》2009,393(6-7):1593-1600
This paper describes a microtip-based approach of concentrating target analytes for a highly sensitive bioassay. As an example, rapid screening of bacterial whole cells is presented to detect Mycobacterium tuberculosis (MTB), a pathogenic bacterium for human tuberculosis (TB). The concentration and detection is performed with three sequential steps of (1) attracting bacterial whole cells in the vicinity of a microtip by alternating current electroosmotic flow; (2) capturing the cells onto the microtip by capillary action; (3) binding fluorophore-labeled polyclonal antibodies to the cells followed by fluorescence measurement (immunofluorescence). Through this mechanism, MTB cells have been detected to the concentration of 8,000 cells/mL within 10 min. This sensitivity is comparable to that of Ziehl–Neelsen smear microscopy, a common culture-free screening method for diagnosis of TB. For comparison, Escherichia coli O157:H7 cells have also been detected to the concentration of 30,000 cells/mL in the same way. 相似文献
4.
An experimental investigation was conducted to determine the influence of postmold trimming and resultant edge quality on
the performance of fiber-reinforced plastics (FRP) under dynamic loads. Graphite/epoxy and graphite/bismaleimide laminates
were machined using three state-of-the-art industrial techniques and subjected to three-point bend impact to failure. The
load load-line displacement records were used to obtain the load, bend deflection and energy absorbed to fracture. High-speed
photography was also employed to identify the initiation and progression of failure and record the time dependent fracture
process. From a comparison of edge quality and subsequent material performance for both polymeric composites, it was found
that the impact response of FRPs is highly process dependent. In general, the load and energy absorbed to fracture decreases
with increasing surface roughness. Reductions in the load and energy to the onset of fracture with degrading surface quality
were as high as 20 percent. The dynamic response was also found to be dependent on the constituents, stacking sequence and
impact velocity. 相似文献
5.
Javier Rodríguez-Rodríguez Carolina Marugán-CruzAlberto Aliseda Juan Carlos Lasheras 《Experimental Thermal and Fluid Science》2011,35(2):301-310
The flow near the leading edge of a steady breaker has been studied experimentally using Bubble Image Velocimetry (BIV) with the aim of characterizing the dynamics of the large eddies responsible for air entrainment. It is well reported in the literature, and confirmed by our measurements of the instantaneous velocity field, that this flow shares some important features with the turbulent shear-layer formed between two parallel semi-infinite streams with different velocities. Namely, the formation of a periodic array of coherent vortices, the constant convective velocity of those vortices, the linear relation between their size and their downstream position and the self-similar structure of both mean velocity profiles and Reynolds shear stresses. Nonetheless, important differences exists between the dynamics of the large eddies in a steady breaker and those in a free shear-layer. Particularly, the convective velocity of these large structures is slower in a steady breaker and, consistent with this, their growth rates are larger. A physical interpretation of these differences is provided together with a discussion of their implications. To support our measurements and conclusions, we present a careful analysis of the accuracy of the BIV technique in turbulent flows with large bubbles. 相似文献
6.
Giulio G. Giusteri 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2013,64(2):371-380
It is well known that second-gradient continuum mechanical theories allow for the appearance of concentrated stresses along the edges of piecewise smooth material surfaces, but this is not the sole example of concentrated interaction. Two additional kinds of concentrated interaction are shown to take place in some second-gradient incompressible dissipative fluids: the adherence to one-dimensional immersed bodies and the capability of sustaining concentrated external body forces. These three phenomena turn out to be distinct and independent. This feature is explicitly discussed in two benchmark problems, and the different mathematical origins of each concentrated interaction are explained. 相似文献
7.
We describe an experimental setup aimed at studying turbulent-induced droplet collisions in a laboratory setting. Our goal is to reproduce conditions relevant to warm-rain formation in clouds. In these conditions, the trajectories of small inertial droplets are strongly influenced by the background air turbulence, and collisions can potentially explain the droplet growth rates and spectrum broadening observed in this type of clouds. Warm-rain formation is currently under strong scrutiny because it is an important source of uncertainty in atmospheric models. A grid at the entrance of a horizontal wind tunnel produces homogeneous isotropic turbulence at a Re λ in the range of 400–500. Water droplets are injected from the nodes of the turbulence-inducing grid at a volume fraction (?) of 2.7?×?10?5 and with sizes of 10–200?μm. A complex manifold-injection system was developed to obtain uniform water droplet seeding, in terms of both water content and size distribution. We characterize the resulting droplet-laden turbulent flow, and the statistics of droplet pairs are measured and analyzed. We found that the radial distribution function (RDF), a measure of preferential concentration of droplets that plays a key role in collision kernel models, has a large peak at distances below the Kolmogorov microscale of the turbulence. At very long separations, comparable with the integral length scale of the turbulence, these RDFs show a slow decay to the average probability given by the mean droplet number density. Consistent with this result, conditional analysis shows an increased local concentration of droplets within the inertial length scale (≈ 10–100 Kolmogorov lengths). These results are in good agreement with previous experiments that found clustering of inertial droplets with St?≈ 1 at scales on the order of 10η. Ultimately, our results support the hypothesis that turbulence-induced preferential concentration and enhanced settling can lead to significant increases in the collision probability for inertial droplets in the range 10–50?μm. 相似文献
8.
The lumbar intervertebral disc, the apparent nexus of low back pain, undergoes biomechanical changes during its degeneration
which are as yet poorly understood. In an effort to ultimately examine in vivo daily activity loads across intervertebral discs, we engaged in the following methodological study. The aim of this research
was to correlate vertebral body surface strains with the loads across a lumbar spine segment. Rosette strain gages were affixed
anterolaterally on L4 and L5 in a macaque monkey model. These tissues were loaded axially and with sagittal plane moments
and the principal strains were compared with the applied loads. Predictable axial and sagittal plane loading profiles were
found for similar strain measurements and the system was found to be robust through freezing and thawing. These results support
future research aimed at quantifying the in vivo disc mechanics of healthy and degenerate tissues in an attempt to develop prevention or intervention strategies to ease those
afflicted with low back pain. 相似文献
9.
Kim JH Yeo WH Shu Z Soelberg SD Inoue S Kalyanasundaram D Ludwig J Furlong CE Riley JJ Weigel KM Cangelosi GA Oh K Lee KH Gao D Chung JH 《Lab on a chip》2012,12(8):1437-1440
A rapid, accurate tuberculosis diagnostic tool that is compatible with the needs of tuberculosis-endemic settings is a long-sought goal. An immunofluorescence microtip sensor is described that detects Mycobacterium tuberculosis complex cells in sputum in 25 minutes. Concentration mechanisms based on flow circulation and electric field are combined at different scales to concentrate target bacteria in 1 mL samples onto the surfaces of microscale tips. Specificity is conferred by genus-specific antibodies on the microtip surface. Immunofluorescence is then used to detect the captured cells on the microtip. The detection limit in sputum is 200 CFU mL(-1) with a success rate of 96%, which is comparable to PCR. 相似文献
10.
A biaxially loaded, single edge notched (SEN) fracture specimen, with mixed modes I and II loading, was used to study the
crack arrest capability of a bonded and riveted tear strap without and with simulated multiple site damage (MSD). MSD was
modeled by a 50-percent groove without which the running crack would inevitably kink due to KII loading. A total of thirty-one 2024-T3 aluminum specimens with various crack and MSD configurations were tested. The fracture
parameters associated with straight and curved crack paths were determined by using the experimenta results to drive a dynamic
finite element model of the specimen in its generation mode. The crack kinking and extension criteria were verified by the
excellent agreement between the prediction based on these fracture parameters and the measured crack kinking angles. Comparison
between the test results generated by the biaxial stress specimens and by those generated by small- and full-scale pressurized
fuselage rupture experiments showed that this specimen can be used to prescreen the effectiveness of tear straps and crack
arrestors in an airplane fuselage. 相似文献