What are the differences in driver injury outcomes at highway-rail grade crossings? Untangling the role of pre-crash behaviors

Crashes at highway-rail grade crossings can result in severe injuries and fatalities to vehicle occupants. Using a crash database from the Federal Railroad Administration (N = 15,639 for 2004–2013), this study explores differences in safety outcomes from crashes between passive controls (Crossbucks and STOP signs) and active controls (flashing lights, gates, audible warnings and highway signals). To address missing data, an imputation model is developed, creating a complete dataset for estimation. Path analysis is used to quantify the direct and indirect associations of passive and active controls with pre-crash behaviors and crash outcomes in terms of injury severity. The framework untangles direct and indirect associations of controls by estimating two models, one for pre-crash driving behaviors (e.g., driving around active controls), and another model for injury severity. The results show that while the presence of gates is not directly associated with injury severity, the indirect effect through stopping behavior is statistically significant (95% confidence level) and substantial. Drivers are more likely to stop at gates that also have flashing lights and audible warnings, and stopping at gates is associated with lower injury severity. This indirect association lowers the chances of injury by 16%, compared with crashes at crossings without gates. Similar relationships between other controls and injury severity are explored. Generally, crashes occurring at active controls are less severe than crashes at passive controls. The results of study can be used to modify Crash Modification Factors (CMFs) to account for crash injury severity. The study contributes to enhancing the understanding of safety by incorporating pre-crash behaviors in a broader framework that quantifies correlates of crash injury severity at active and passive crossings.     

Glass waste as supplementary cementing materials: The effects of glass chemical composition

Sustainable cements containing 25 wt% of different types of recycled glass have been investigated as a supplementary cementing material in order to highlight the role of glass chemical composition during the hardening process. Glass formers, stabilizers and modifiers regulate the glass dissolution in the alkaline environment during cement hydration. As a consequence, pozzolanic reaction and/or alkali–silica reaction are strictly related to the glass chemical composition. The mechanical and microstructure characterizations of mortar samples containing glass blended cements and un-reactive aggregates allow to determine which oxides in the glass have to be carefully monitored to avoid deleterious reactions.     

Transparent and flexible films of new segmented polyurethane nanocomposites incorporated by NH2-functionalized TiO2 nanoparticles

In this work, TiO₂ nanoparticles are surface modified by NH₂-terminated organic moieties arised from 4,4′-methylene diphenyl diisocyanate (MDI). These nanoparticles are incorporated into ether-based segmented polyurethane (SPU) matrix. MDI is utilized as monomer together with poly(tetramethylene oxide) (PTMO) comonomer for preparing the final polymer as well. The NH₂-functionalized TiO₂ nanoparticles are covalently linked to the NCO terminals of the resulting SPU macromolecules during film preparation stage. Therefore, in addition to butylene glycol, these surface modified nanoparticles with enhanced organophilicity could play the role of the second chain extender of NCO-capped SPU macromolecules through formation of urea linkages. Optical and thermal behaviors of the transparent and flexible film (SPU/TiO₂–MDI) is compared with those of unmodified TiO₂ (SPU/TiO₂) and TiO₂-unloaded SPU films. Though the particle loading is only 5 wt.%, incorporation of TiO₂ and TiO₂–MDI nanoparticles into the SPU polymer enhances significantly the light absorption in UV region at 300–400 nm. SEM images of the prepared films clearly show a considerable decrease in particle aggregation for TiO₂–MDI into SPU matrix compared to that of unmodified TiO₂. TG analyses indicate a one-step decomposition pattern with onset temperatures of about 360 and 380 °C for neat SPU and SPU/TiO₂–MDI, respectively. Moreover, DTA thermograms of both nanocomposites show obviously two exothermic phase transitions in the thermal range of 330–440 °C.     

初创型团队异质性与团队创新的关系:基于团队外部知识网络的视角

目的探索基于团队外部知识网络视角来考察年龄异质性和专业异质性对初创型异质性团队创新的作用。方法采用问卷调查的方法。对102个初创型团队进行调查。结果在初创型团队中,年龄异质性和专业异质性均能提升团队创新,外部知识网络利用强度和广度在年龄异质性促进团队创新的过程中承担中介作用,外部知识网络利用强度在专业异质性促进团队创新的过程中承担中介作用。结论在初创型团队中,年龄异质性通过提升外部知识网络利用促进团队创新,专业异质性通过提升外部知识网络利用强度促进团队创新。     

Acoustic emission analysis using Bayesian model selection for damage characterization in ceramic matrix composites

Acoustic emission (AE) during tensile testing of three-dimensional woven SiC/SiC composites was analyzed by a statistical modeling method based on a Bayesian approach to quantitatively evaluate the fracture process. Gaussian mixture models and Weibull mixture models were utilized as candidate models describing the AE time-series data. After fitting AE time-series data to these models with Markov Chain Monte Carlo (MCMC) methods, the model selection was conducted by stochastic complexity. Among the candidate models, the two-component Weibull mixture model was automatically selected. It was confirmed that the component distributions in the two-component Weibull mixture model were corresponding to the evolution of matrix cracking and fiber breakage, respectively. Since the proposed AE analysis method can determine the number of component distributions without the decision of researchers and inspectors, it is expected to be useful for an understanding of the fracture process in newly developed materials and the reliability assessment in service.     

New observations on wear characteristics of solid Al2O3/Si3N4 ceramic tool in high speed milling of additive manufactured Ti6Al4V

Additive Manufacturing (AM) technologies applied to the titanium alloys have attracted attention from industries in recent years. Despite one of the main goals of AM is the reduction of manufacturing steps, semi-finish/finish machining operations are still required so as to obtain the desired geometrical tolerance and surface features. In this study, the solid end mill was manufactured by Al₂O₃/Si₃N₄ (Sialon) ceramic materials and employed in high-speed slot milling of Ti6Al4V alloy fabricated by the Direct Metal Laser Sintering (DMLS) AM technology to study the tool wear characteristics during processing. The Raman spectroscopic method was employed to characterize the molecular structures of Sialon ceramics for the manufacturing of the cutting tool. The morphologies and elemental maps of wear region of the ceramic tool were examined by scanning electron microscope and energy dispersive spectroscopy techniques. The results show that the adhesion wear and diffusion wear are the dominant wear mechanisms, and the chemical stability of Al₂O₃/Si₃N₄ (Sialon) ceramics fabricated as the solid ceramic tool to the attack of the atoms from additive manufactured Ti6Al4V is relatively weak under the atmosphere. The difference of thermal expansion coefficients of diffusion layer and tool substrate accelerates the initiation and propagation of thermal cracks formed on the diffusion interface. Moreover, fracturing and crater-like groves near the tool edge were finally formed due to the removal of adhered workpiece material.     

Droplet behaviors on inclined surfaces with dynamic contact angle

Dynamic contact angle (DCA) is of crucial importance in the numerical investigation of water management problems in proton exchange membrane fuel cells (PEMFCs). In order to well predict the gas-liquid two-phase flow in the complex flow field in PEMFCs, first, it is very critical to build a robust DCA model that is capable of simulating droplet behaviors on a single surface under various conditions. In our previous research work, an advancing-receding DCA (AR-DCA) model is developed and has been successfully validated against a series of experiments from the available literature for droplet impact on surfaces. In this study, the AR-DCA model is further applied to simulate droplet behaviors on inclined surfaces with different droplet impact velocities, impact angles and viscosities. It is found that the droplet spreading and deformation from the simulations have excellent agreement with those captured in the corresponding experiments. The results also indicate that higher impact velocity and impact angle can facilitate the spreading trend at the droplet trailing edge and have no notable effects on the leading edge. In addition, the increase of droplet viscosity leads to a transition from droplet deposition phenomenon to partial rebound on the surface.     

认知闭合需要对农户规范施药行为的影响研究——基于信息加工的中介效应

文章利用辽宁省农户微观调查数据,从认知心理学角度应用结构方程模型分析了认知闭合需要对施药行为的影响机理。研究结果表明:认知闭合需要水平越高,农户施药行为越不规范。具体而言,规则性偏好和确定性偏好程度越高,其施药行为的规范性越低;心理封闭对农户施药行为没有显著影响。同时,认知闭合需要对农户施药行为具有间接影响,且在规则性偏好和确定性偏好对施药行为的间接影响中,信息加工产生了中介效应。     

Biphenyl liquid crystal epoxy containing flexible chain: Synthesis and thermal properties

A biphenyl type liquid crystal epoxy (LCE) monomer 4,4′-di(2,3-epoxyhexyloxy)biphenyl (LCBP4) containing flexible chain was synthesized and the curing behavior was investigated using 4,4′-diaminodiphenylmethane (DDM) as the curing agent. The effect of curing condition on the formation of the liquid crystalline phase was examined. The cured samples show good mechanical properties and thermal stabilities. Moreover, the relationship between thermal conductivity and structure of liquid crystalline domain was also discussed. The samples show high thermal conductivity up to 0.28–0.31 W/(m*K), which is 1.5 times as high as that of conventional epoxy systems. In addition, thermal conductive filler, Al₂O₃, was introduced into LCBP4/DDM to obtain higher thermal conductive composites. When the content of Al₂O₃ was 80 wt%, the thermal conductivity of the composite reached to 1.86 W/(m*K), while that of diglycidyl ether of bisphenol A (Bis-A) epoxy resin/DDM/Al₂O₃ was 1.15 W/(m*K). Compared with Bis-A epoxy resin, the formation of liquid crystal domains in the cured LCE resin enhanced the thermal conductivity synergistically with the presence of Al₂O₃. Furthermore, the introduction of Al₂O₃ also slightly increased the thermal stabilities of the cured LCE.     

Yes I can cook a fish; effects of a five week sensory-based experiential theme course with fish on 11- to 13- year old children’s food literacy and fish eating behaviour – A quasi-experimental study

Danish early-phase adolescents only consume one-third of the officially recommended amount of fish. The objective of this study is to investigate the effect of a five week sensory-based experiential theme course with fish on 11- to 13-year old early-phased adolescents’ food literacy and acceptance of fish. Study design was a quasi-experimental intervention. 32 Food Knowledge school classes were recruited from the eastern part of Denmark. Classes were assigned to intervention group (n = 185), control group 1 (n = 123), only baseline and follow-up survey, or control group 2 (n = 75): one oral lecture between baseline and follow-up survey. Mixed methods strategy was applied: baseline and follow-up survey, participant observation, telephone-, and group interviews. Before between study group analysis control groups were pooled. The following key effects of the intervention were observed: knowledge on fish and cooking increased within specific areas, skills related to fish and cooking increased, especially in girls. Furthermore, the social dimension and helping each other were important elements. In the intervention group no positive effects were observed for liking or assessment of fish disgust; however, theme course evaluation showed that 47% had become curious on tasting other kinds of fish and 38% stated a higher liking for fish after participation. Furthermore, teachers reported an increase in acceptance of fish in the children as a result of participating. In conclusion food literacy and fish acceptance were increased through participation in a five week sensory-based experiential theme course with fish.