Modeling and interpretation of fiber orientation-based failure mechanisms in machining of carbon fiber-reinforced polymer composites

The development and implementation of a microstructure-based finite element model for the machining of carbon fiber-reinforced polymer composites is presented. A new approach to interfacial modeling is introduced where the material interface is modeled using continuum elements, allowing failure to take place in either tension or compression. The model is capable of describing the fiber failure mode occurring throughout the chip formation process. Characteristic fiber length in the chips, and machining forces for microstructures with fibers orientated at 0°, 45°, 90°, and 135° are examined. For model validation purposes, the model-based machining performance predictions are compared to the machining responses from a set of orthogonal machining experiments. A parametric study is presented that identifies a robust tool geometry, which minimizes the effects of fiber orientation and size on the machining forces.     

Automated micro-transfer printing with cantilevered stamps

This paper demonstrates the use of a flexible instrumented stamp to enable automated micro transfer printing as a route to large-area, deterministic assembly of microstructured device components or ‘inks’. The ability to instrument the stamp, a critical component for retrieval and placement of a micro device, to detect contact and monitor localized forces during critical events in the printing process not only allows for the development of a robust manufacturing process, but also for a unique vantage point from which to study fundamental issues and phenomena associated with adhesion and delamination of thin films from a variety of substrate materials. This paper presents basic design analysis on the requirements of the cantilevers for compatibility with a typical transfer printing environment. Off-the-shelf thin film strain gages are integrated with a thin elastomeric post as a preliminary prototype and the feasibility of transfer printing with it is demonstrated. Further, the set-up is calibrated to produce force signals for event detection and in situ diagnosis of the process.     

Does safety climate moderate the influence of staffing adequacy and work conditions on nurse injuries?

PROBLEM: Hospital nurses have one of the highest work-related injury rates in the United States. Yet, approaches to improving employee safety have generally focused on attempts to modify individual behavior through enforced compliance with safety rules and mandatory participation in safety training. We examined a theoretical model that investigated the impact on nurse injuries (back injuries and needlesticks) of critical structural variables (staffing adequacy, work engagement, and work conditions) and further tested whether safety climate moderated these effects. METHOD: A longitudinal, non-experimental, organizational study, conducted in 281 medical-surgical units in 143 general acute care hospitals in the United States. RESULTS: Work engagement and work conditions were positively related to safety climate, but not directly to nurse back injuries or needlesticks. Safety climate moderated the relationship between work engagement and needlesticks, while safety climate moderated the effect of work conditions on both needlesticks and back injuries, although in unexpected ways. DISCUSSION AND IMPACT ON INDUSTRY: Our findings suggest that positive work engagement and work conditions contribute to enhanced safety climate and can reduce nurse injuries.     

Further evidence of nuclear reactions in the Pd/D lattice: emission of charged particles

Almost two decades ago, Fleischmann and Pons reported excess enthalpy generation in the negatively polarized Pd/D-D₂O system, which they attributed to nuclear reactions. In the months and years that followed, other manifestations of nuclear activities in this system were observed, viz. tritium and helium production and transmutation of elements. In this report, we present additional evidence, namely, the emission of highly energetic charged particles emitted from the Pd/D electrode when this system is placed in either an external electrostatic or magnetostatic field. The density of tracks registered by a CR-39 detector was found to be of a magnitude that provides undisputable evidence of their nuclear origin. The experiments were reproducible. A model based upon electron capture is proposed to explain the reaction products observed in the Pd/D-D₂O system.

Choice of teenagers' vehicles and views on vehicle safety: survey of parents of novice teenage drivers

Objective

To examine parental decisions about vehicles driven by teenagers and parental knowledge of vehicle safety.

Methods

About 300 parents were interviewed during spring 2006 in Minnesota, North Carolina, and Rhode Island while teenagers took their first on-road driving tests.

Results

Fewer than half of parents surveyed said teenagers would be the primary drivers of the chosen vehicles. Parents most often cited safety, existing family vehicle, and reliability when explaining the choices for their teenagers’ vehicles. About half of the vehicles intended for teenagers were small/mini/sports cars, pickups, or SUVs — vehicles considered less safe for teenagers than midsize/large cars or minivans. A large majority of vehicles were 2001 models or earlier. Vehicles purchased in anticipation of adding a new driver to the family were more likely to be the sizes/types considered less safe than vehicles already owned. Few parents insisted on side airbags or electronic stability control, despite strong evidence of their safety benefits. Even when asked to identify ideal vehicles for their teenagers to drive, about half of parents identified less safe vehicle sizes/types. Most parents knew that midsize/large vehicles are safer than small vehicles, and at least half of parents said SUVs and pickups are not safe for teenage drivers, citing instability.

Conclusions

The majority of parents understood some of the important criteria for choosing safe vehicles for their teenagers. However, parents actually selected many vehicles for teenagers that provide inferior crash protection.

Impact on industry

Vehicle safety varies substantially by vehicle size, type, and safety features. Many teenagers are driving inferior vehicles in terms of crashworthiness and crash avoidance.     

Secondary analysis of time of day on simulated driving performance

PROBLEM: Age and gender are frequently controlled for in studies of driving performance, but the effects of time of day or circadian cycles on performance are often not considered. Previous research on time of day effects of simulated driving is contradictory and provides little guidance for understanding the impact of these variables on results. METHODS: Using driving simulator data from 79 subjects ages 18 to 65, this paper focuses on the impact of age, gender, and time of day on the simulated driving performance of subjects who self-selected the time of participation. RESULTS: Time of day effects were consistently evident for drivers' speed overall and across different simulated environments. Drivers in the late afternoon period consistently drove significantly slower than drivers in other time periods. Age and gender affected speed such that women and those participants 50 and older tended to drive more slowly. Time of day also had an effect on reaction time and on speed variability measures. Gender did not have significant effects on reaction time or variability measures, but age effects were present. SUMMARY: Taken together, the results suggest that time of day effects should be considered as part of simulated driving performance, and that interactions between time of day and other variables, notably age, should be controlled for as part of future research. IMPACT ON INDUSTRY: Implications of these findings on current efforts for older driver testing are discussed.     

Land use change and forestry climate project regional baselines: a review

Climate change programs have largely used the project-specific approach for estimating baseline emissions of climate mitigation projects. This approach is subjective, lacks transparency, can generate inconsistent baselines for similar projects, and is likely to have high transaction costs. The use of regional baselines, which partially addresses these issues, has been reported in the literature on forestry and agriculture projects, and in greenhouse gas (GHG) mitigation program guidance for them (e.g., WRI/WBCSD GHG Project Protocol, USDOE’s 1605(b) registry, UNFCCC’s Clean Development Mechanism). This paper provides an assessment of project-specific and regional baselines approaches for key baseline tasks, using project and program examples. The regional experience to date is then synthesized into generic steps that are referred to as Stratified Regional Baselines (SRB). Regional approaches generally, and SRB in particular explicitly acknowledge the heterogeneity of carbon density, land use change, and other key baseline driver variables across a landscape. SRB focuses on providing guidance on how to stratify lands into parcels with relatively homogeneous characteristics to estimate conservative baselines within a GHG assessment boundary, by applying systematic methods to determine the boundary and time period for input data.

Cranial shape transformation in the evolution of the giant panda (Ailuropoda melanoleuca)

In this study, landmark-based methods of geometric morphometrics are used for investigating the main aspects of cranial shape transformation in the evolution of the giant panda, Ailuropoda melanoleuca. Specifically, we explore if the highly derived cranial adaptations for bamboo feeding of the living panda were developed early in the panda's lineage. Results obtained show that the overall cranial morphologies of the oldest known panda, the "pygmy" Ailuropoda microta, and the late Pleistocene Ailuropoda baconi are both very similar to that of their closest living relative, A. melanoleuca, which agrees with a previous proposal based on qualitative criteria. However, we also describe several differences between the crania of A. microta, A. baconi, and A. melanoleuca, including the development of the postorbital process, the orientation of the occipital region, and the expansion of the braincase. As a result, the cranial morphology of A. microta shows a less specialized morphology toward a fibrous and durophagous diet compared to the giant panda. These results are confirmed by a comparative analysis of the dimensions of the upper teeth in bears, which has revealed differences in relative tooth size between A. microta and A. melanoleuca, most probably as a result of mosaic evolution. Therefore, we conclude that cranial shape did not remain essentially uniform in the Ailuropoda lineage, as previously thought, but underwent a number of changes during more than 2?Myr.