Morphologically dependent alternating‐current and direct‐current breakdown strength in silica–polypropylene nanocomposites

In this article, we report the synthesis of a new bimodal surface ligand morphology on silica nanoparticles. Combining grafting‐to and grafting‐from approaches, in this study, we demonstrated the efficacy of anthracene surface modification for improving the dielectric breakdown strength (DBS) under alternating‐current and direct‐current conditions and that of a matrix‐compatible polymer brush for controlling the nanofiller (NF) dispersion. Ligand‐modified spherical colloidal SiO₂ nanoparticles (～14 nm in diameter) were mixed into polypropylene, and the resulting dispersion was improved over the unmodified particles, as shown with transmission electron microscopy. The results suggest that the electronic structure of the anthracene‐modified particle surface was critical to the improvement in DBS. In addition, the DBS of the composite was shown to depend on the dispersion state of the filler and the mode of stress; this indicated that the individually dispersed nanoparticles were not necessarily the optimal morphology for all stress conditions. Additionally, the precise nature of the matrix‐compatible brush was less important than the NF dispersion it produced. The bimodal grafted architectural design has provided a promising solution for the control of the dispersion and surface properties, especially for high‐molecular‐weight polymer matrices. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44347.     

Reliability-Based Design Optimization for Durability of Ground Vehicle Suspension System Components

The effect of materials processing- and component manufacturing-induced uncertainties in material properties and component shape and size on the reliability of component performance is investigated. Specifically, reliability of a suspension system component from a high-mobility multipurpose wheeled vehicle which typically can fail under low-cycle strain-based fatigue conditions is analyzed. Toward that end, the most advanced reliability-based design optimization methods available in the literature were combined with the present understanding of low-cycle fatigue durability and applied to the component in question. This entailed intricate integration of several computational tools such as multibody vehicle dynamics, finite-element simulations, and fatigue strain-life assessment/prediction techniques. The results obtained clearly revealed the importance of consideration of material property uncertainties in attaining vehicle performance of critical structural components in complex systems (e.g., a vehicle).     

Comparing the effectiveness of several modeling methods for fault prediction

We compare the effectiveness of four modeling methods—negative binomial regression, recursive partitioning, random forests and Bayesian additive regression trees—for predicting the files likely to contain the most faults for 28 to 35 releases of three large industrial software systems. Predictor variables included lines of code, file age, faults in the previous release, changes in the previous two releases, and programming language. To compare the effectiveness of the different models, we use two metrics—the percent of faults contained in the top 20% of files identified by the model, and a new, more general metric, the fault-percentile-average. The negative binomial regression and random forests models performed significantly better than recursive partitioning and Bayesian additive regression trees, as assessed by either of the metrics. For each of the three systems, the negative binomial and random forests models identified 20% of the files in each release that contained an average of 76% to 94% of the faults.     

Enhanced Bioavailability of Eicosapentaenoic Acid from Fish Oil After Encapsulation Within Plant Spore Exines as Microcapsules

Benefits of eicosapentaenoic acid (EPA) can be enhanced by raising their bioavailability through microencapsulation. Pollen can be emptied to form hollow shells, known as exines, and then used to encapsulate material, such as oils in a dry powder form. Six healthy volunteers ingested 4.6 g of fish oil containing 20% EPA in the form of ethyl ester first alone and then as 1:1 microencapsulated powder of exines and fish oil. Serum bioavailability of EPA was measured by area under curve (AUC_0–24). The mean AUC_0–24 of EPA from ethyl ester with exine (M = 19.7, SD = 4.3) was significantly higher than ethyl ester without exines (M = 2, SD = 1.4, p < 0.01).The bioavailability of EPA is enhanced by encapsulation by pollen exines.     

Fluid/Structure Interaction Computational Investigation of Blast-Wave Mitigation Efficacy of the Advanced Combat Helmet

To combat the problem of traumatic brain injury (TBI), a signature injury of the current military conflicts, there is an urgent need to design head protection systems with superior blast/ballistic impact mitigation capabilities. Toward that end, the blast impact mitigation performance of an advanced combat helmet (ACH) head protection system equipped with polyurea suspension pads and subjected to two different blast peak pressure loadings has been investigated computationally. A fairly detailed (Lagrangian) finite-element model of a helmet/skull/brain assembly is first constructed and placed into an Eulerian air domain through which a single planar blast wave propagates. A combined Eulerian/Lagrangian transient nonlinear dynamics computational fluid/solid interaction analysis is next conducted in order to assess the extent of reduction in intra-cranial shock-wave ingress (responsible for TBI). This was done by comparing temporal evolutions of intra-cranial normal and shear stresses for the cases of an unprotected head and the helmet-protected head and by correlating these quantities with the three most common types of mild traumatic brain injury (mTBI), i.e., axonal damage, contusion, and subdural hemorrhage. The results obtained show that the ACH provides some level of protection against all investigated types of mTBI and that the level of protection increases somewhat with an increase in blast peak pressure. In order to rationalize the aforementioned findings, a shockwave propagation/reflection analysis is carried out for the unprotected head and helmet-protected head cases. The analysis qualitatively corroborated the results pertaining to the blast-mitigation efficacy of an ACH, but also suggested that there are additional shockwave energy dissipation phenomena which play an important role in the mechanical response of the unprotected/protected head to blast impact.     

Characterization of film-coated aerosol canisters using electrochemical impedance spectroscopy

Drug adhesion to the walls of an aerosol canister can be prevented/reduced by coating the canister with a hydrophobic polymer (e.g., a fluoropolymer). In this study, three batches of fluoropolymer-coated canisters were investigated by electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The EIS technique showed that only one of the batches presented as a monolithic, non-porous film. The other two batches were either partially porous or highly porous. Scanning electron micrographs showed evidence of cracks, within the films, but could not alone establish the porous nature of these defects. For the non-porous and partly porous films it was possible to use the EIS data to determine the approximate film thickness. Estimates of 2-4 µm were obtained for the mean film thickness. These values compared favorably with micrometer estimates obtained following acid dissolution of the aluminum canister. It remains to be seen whether the properties of the films (i.e., the porosity and film thickness, determined by EIS) translate to differences in drug adhesion. Nevertheless, the EIS technique was shown to be a powerful, non-destructive method that lends itself to the rapid analysis of batch-to-batch variation in film-coated canisters.     

Relationships among team ability composition, team mental models, and team performance.

This study examined the relationship between the similarity and accuracy of team mental models and compared the extent to which each predicted team performance. The relationship between team ability composition and team mental models was also investigated. Eighty-three dyadic teams worked on a complex skill task in a 2-week training protocol. Results indicated that although similarity and accuracy of team mental models were significantly related, accuracy was a stronger predictor of team performance. In addition, team ability was more strongly related to the accuracy than to the similarity of team mental models and accuracy partially mediated the relationship between team ability and team performance, but similarity did not. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

运营商可信赖的3G伙伴--上海贝尔阿尔卡特

对于3G网络运营商来说，网络是其最重要的竞争资源，低成本、高质量的3G网络是其成功运营获得丰厚利润的基础。因此，设备供应商是3G网络运营商在整个价值链上最为重要的合作伙伴。一个值得运营商长期信赖的3G网络设备供应商应该具有如下四个方面的特征：成熟的网络解决方案、出色的网络规划与优化、丰富的应用业务支持和强大的综合实力。     

Influences Impacting Leadership Development

The construction industry is placing increased emphasis on developing leadership skills for project managers. This paper describes a research project that was executed to analyze the causal influences on the development of project managers, whom the authors believe also must be leaders. The research compared two groups of project managers within a large construction company. One group was top performing construction managers as selected by corporate executives, while the second group was a randomly selected control group. The research examined influences on career development including job experience, project management experience, formal project management training, formal leadership training, and job assignments. The research also solicited opinions from both groups as to what they perceived as factors impacting leadership career development. Statistical differences between the groups were found in the areas of project management experience and number of positions held prior to the first project management assignment. Both groups believed there was more of a need within their company for leadership training than for project management training.