A Supplemental Analysis of Selected Two-Vehicle Front-to-Rear Collisions from the NASS/CDS

The National Automotive Sampling System/Crashworthiness Database System (NASS/CDS) is a well-known digital repository containing statistics on hundreds of thousands of vehicle crashes that occurred over the past 30 years. Many of the NASS crashes contain estimates of Delta-v calculated using WinSMASH, a common software reconstruction package. Recent work indicates that WinSMASH typically underestimates Delta-v in frontal impacts, and that inclusion of restitution significantly improves the estimate of Delta-v to within 1% of the value recorded on EDR-equipped vehicles [1]. Prior experiments have shown that in front-to-rear collisions, restitution is a strong inverse function of closing velocity (the difference between the respective pre-impact speeds in the bullet and target vehicles) [2], with calculated restitutions ranging from 0.265 down to 0.0 for closing speeds varying from 11.4 mph to as high as 36 mph. This work uses front-to-rear impact data from the NASS/CDS to examine the effect of coefficient of restitution on calculated Delta-v values for both the bullet and target vehicles. The WinSMASH-based values of Delta-v and dissipated energy contained in the NASS/CDS were compared to Delta-v values computed using traditional analytical (energy and momentum) equations. With restitution set equal to zero, the mean value of the calculated values of Delta-v (for bullet and target vehicles) ranged between −1.76 and 1.47 percent of the values contained in the NASS/CDS. However, including values of restitution computed iteratively using pre-impact closing velocity increased the computed values of Delta-v for both bullet and target vehicles by an average of 10.38 - 13.17 percent over those provided (in the absence of restitution) by the NASS/CDS. In addition, it was found that small errors in reported values of vehicle mass or dissipated energy (2% - 10%) produced similar or smaller percentage variations in calculated Delta-v values for both the bullet and target vehicles

Reduction of Vibration Transmission in String Trimmers

It has been well documented that over long periods of time, people who regularly operate hand tools powered by small internal-combustion engines can become affected by a debilitating set of clinically irreversible effects, collectively referred to as hand-arm vibration syndrome (HAVS). Although HAVS cannot be cured, the onset of the disorder can be delayed or, in fact, prevented, by restricting either the duration of the exposure, and/or the magnitude of the vibration transmitted from the tool to an operator\u27s hands and arms (per ANSI and similar standards). In this paper, we’ve evaluated an approach for reducing the magnitude of transmitted vibration at the engine-side grip of one commercial- and one consumer-grade string trimmer. The ultimate goal of this work is to develop a set of simple, passive retrofits for these tools that will reduce the likelihood of HAVS in full-time grounds-maintenance workers. The idea for this work stems from a stated need of Goodwill Industries of San Antonio, our NPA (non-profit agency) collaborator over the past several years. Based on this preliminary work, we’ve found that grips incorporating half-inch rubber studs placed at areal densities of either 25/in2 or 12/in2 significantly reduce the RMS vibration transmitted to the hand and arm at all frequencies (including the low frequency components known to be most harmful)

The Incredible Shrinking Dewlap: Signal Size, Skin Elasticity, and Mechanical Design in the Green Anole Lizard (Anolis Carolinensis)

The expression of male secondary sexual traits can be dynamic, changing size, shape, color, or structure over the course of different seasons. However, the factors underlying such changes are poorly understood. In male Anolis carolinensis lizards, a morphological secondary sexual signal called the dewlap changes size seasonally within individuals. Here, we test the hypothesis that seasonal changes in male dewlap size are driven by increased use and extension of the dewlap in spring and summer, when males are breeding, relative to the winter and fall. We captured male green anole lizards prior to the onset of breeding and constrained the dewlap in half of them such that it could not be extended. We then measured dewlap area in the spring, summer, and winter, and dewlap skin and belly skin elasticity in summer and winter. Dewlaps in unconstrained males increase in area from spring to summer and then shrink in the winter, whereas the dewlaps of constrained males consistently shrink from spring to winter. Dewlap skin is significantly more elastic than belly skin, and skin overall is more elastic in the summer relative to winter. These results show that seasonal changes in dewlap size are a function of skin elasticity and display frequency, and suggest that the mechanical properties of signaling structures can have important implications for signal evolution and design

Three-dimensional Acceleration Measurement Using Videogrammetry Tracking Data

In order to evaluate the feasibility of multi-point, non-contact, acceleration measurement, a high-speed, precision videogrammetry system has been assembled from commercially-available components and software. Consisting of three synchronized 640 X 480 pixel monochrome progressive scan CCD cameras each operated at 200 frames per second, this system has the capability to provide surface-wide position-versus-time data that are filtered and twice-differentiated to yield the desired acceleration tracking at multiple points on a moving body. The oscillating motion of targets mounted on the shaft of a modal shaker were tracked, and the accelerations calculated using the videogrammetry data were compared directly to conventional accelerometer measurements taken concurrently. Although differentiation is an inherently noisy operation, the results indicate that simple mathematical filters based on the well-known Savitzky and Golay algorithms, implemented using spreadsheet software, remove a significant component of the noise, resulting in videogrammetry-based acceleration measurements that are comparable to those obtained using the accelerometers

Measuring the Performance of Online Distributed Team Innovation (Learning) Services

Copyright c○2004 by the authors. Leifer et al.: Measuring the Performance of Online Distributed Team Innovation

Mycobacterial PIMs Inhibit Host Inflammatory Responses through CD14-Dependent and CD14-Independent Mechanisms

Mycobacteria develop strategies to evade the host immune system. Among them, mycobacterial LAM or PIMs inhibit the expression of pro-inflammatory cytokines by activated macrophages. Here, using synthetic PIM analogues, we analyzed the mode of action of PIM anti-inflammatory effects. Synthetic PIM1 isomer and PIM2 mimetic potently inhibit TNF and IL-12 p40 expression induced by TLR2 or TLR4 pathways, but not by TLR9, in murine macrophages. We show inhibition of LPS binding to TLR4/MD2/CD14 expressing HEK cells by PIM1 and PIM2 analogues. More specifically, the binding of LPS to CD14 was inhibited by PIM1 and PIM2 analogues. CD14 was dispensable for PIM1 and PIM2 analogues functional inhibition of TLR2 agonists induced TNF, as shown in CD14-deficient macrophages. The use of rough-LPS, that stimulates TLR4 pathway independently of CD14, allowed to discriminate between CD14-dependent and CD14-independent anti-inflammatory effects of PIMs on LPS-induced macrophage responses. PIM1 and PIM2 analogues inhibited LPS-induced TNF release by a CD14-dependent pathway, while IL-12 p40 inhibition was CD14-independent, suggesting that PIMs have multifold inhibitory effects on the TLR4 signalling pathway

On a mechanical nondestructive test for integrated circuit TAB bonds and similar solid structures

Mechanical Engineerin