Volpe National Transportation Systems Center

In this article, we build on and extend research into the cognitions and values of users and designers by proposing a systematic approach for examining the underlying assumptions, expectations, and knowledge that people have about technology. Such interpretations of technology (which we call technological frames) are central to understanding technological development, use, and change in organizations. We suggest that where the technological frames of key groups in organizations—such as managers, technologists, and users— are significantly different, difficulties and conflict around the development, use, and change of technology may result. We use the findings of an empirical study to illustrate how the nature, value, and use of a groupware technology were interpreted by various organizational stakeholders, resulting in outcomes that deviated from those expected. We argue that technological frames offer an interesting and useful analytic perspective for explaining an anticipating actions and meanings that are not easily obtained with other theoretical lenses.

Cognitive engineering needs viable constructs and principles to promote better understanding and prediction of human performance in complex systems. Three human cognition and performance constructs that have been the subjects of much attention in research and practice over the past three decades are situation awareness (SA), mental workload, and trust in automation. Recently, Dekker and Woods (2002) and Dekker and Hollnagel (2004; henceforth DWH) argued that these constructs represent “folk models” without strong empirical foundations and lacking scientific status. We counter this view by presenting a brief description of the large science base of empirical studies on these constructs. We show that the constructs can be operationalized using behavioral, physiological, and subjective measures, supplemented by computational modeling, but that the constructs are also distinct from human performance. DWH also caricatured as “abracadabra” a framework suggested by us to address the problem of the design of automated systems (Parasuraman, Sheridan, & Wickens, 2000). We point to several factual and conceptual errors in their description of our approach. Finally, we rebut DWH's view that SA, mental workload, and trust represent folk concepts that are not falsifiable. We conclude that SA, mental workload, and trust are viable constructs that are valuable in understanding and predicting human-system performance in complex systems.

A meta-analysis to mathematically summarize the effect of hot and cold temperature exposure on performance was completed. The results from 515 effect sizes calculated from 22 original studies suggest that hot and cold temperatures negatively impact performance on a wide range of cognitive-related tasks. More specifically, hot temperatures of 90 degrees F (32.22 degrees C) Web Bulb Globe Temperature Index or above and cold temperatures of 50 degrees F (10 degrees C) or less resulted in the greatest decrement in performance in comparison to neutral temperature conditions (14.88% decrement and 13.91% decrement, respectively). Furthermore, the duration of exposure to the experimental temperature, the duration of exposure to the experimental temperature prior to the task onset, the type of task and the duration of the task had differential effects on performance. The current results indicate that hot and cold temperature exposure have a negative impact on performance and that other variables (e.g., length of exposure to the temperature or task duration) may modify this relationship.

Abstract. The global commercial aircraft fleet in 2006 flew 31.26 million flights, burned 188.20 million metric tons of fuel, and covered 38.68 billion kilometers. This activity emitted substantial amounts of fossil-fuel combustion products within the upper troposphere and lower stratosphere that affect atmospheric composition and climate. The emissions products, such as carbon monoxide, carbon dioxide, oxides of nitrogen, sulfur compounds, and particulate matter, are not emitted uniformly over the Earth, so understanding the temporal and spatial distributions is important for modeling aviation's climate impacts. Global commercial aircraft emission data for 2004 and 2006, provided by the Volpe National Transportation Systems Center, were computed using the Federal Aviation Administration's Aviation Environmental Design Tool (AEDT). Continuous improvement in methodologies, including changes in AEDT's horizontal track methodologies, and an increase in availability of data make some differences between the 2004 and 2006 inventories incomparable. Furthermore, the 2004 inventory contained a significant over-count due to an imperfect data merge and daylight savings error. As a result, the 2006 emissions inventory is considered more representative of actual flight activity. Here, we analyze both 2004 and 2006 emissions, focusing on the latter, and provide corrected totals for 2004. Analysis of 2006 flight data shows that 92.5% of fuel was burned in the Northern Hemisphere, 69.0% between 30N and 60N latitudes, and 74.6% was burned above 7 km. This activity led to 162.25 Tg of carbon from CO2 emitted globally in 2006, more than half over three regions: the United States (25.5%), Europe (14.6), and East Asia (11.1). Despite receiving less than one percent of global emissions, the Arctic receives a uniformly dispersed concentration of emissions with 95.2% released at altitude where they have longer residence time than surface emissions. Finally, 85.2% of all flights by number in 2006 were short-haul missions, yet those flights were responsible for only 39.7% of total carbon from CO2. The following is a summary of these data which illustrates the global and regional aviation emissions footprints for 2004 and 2006, and provides temporal and spatial distribution statistics.

Advanced traffic management systems (ATMS) and advanced traveler information systems (ATIS) are promising technologies for achieving efficiency in the operation of transportation systems. A simulation-based laboratory environment, MITSIMLab, is presented that is designed for testing and evaluation of dynamic traffic management systems. The core of MITSIMLab is a microscopic traffic simulator (MITSIM) and a traffic management simulator (TMS). MITSIM represents traffic flows in the network, and the TMS represents the traffic management system under evaluation. An important feature of MITSIMLab is its ability to model ATMS or ATIS that generate traffic controls and route guidance based on predicted traffic conditions. A graphical user interface allows visualization of the simulation, including animation of vehicle movements. An ATIS case study with a realistic network is also presented to demonstrate the functionality of MITSIMLab.

Rats subjected to transient forebrain ischemic injury by the method of four vessel occlusion (4-VO) develop irreversible injury to select populations of vulnerable neurons which include pyramidal cells in the CA-1 region of the hippocampus. This brain area is thought to be crucial for learning and memory. Rats subjected to 30 minutes of 4-VO, and then cerebral reperfusion were tested on a radial 8-arm maze task after they had recovered. The data shows that both 4-VO and control animals improve their performance over trials, but that 4-VO rats are impaired on "working" and "reference" tasks. The data suggest that 4-VO rats' impaired "working" performance is permanent, compared to their transient "reference" impairment. Alterations in sensorimotor activity could not account for these performance deficits since control and 4-VO rats demonstrated equivalent choice time per maze arm. Performance deficits in rats following forebrain ischemic injury may be similar to some of the cognitive deficits found in humans survivors of cerebral hypoxia-ischemia.

RATIONALE: Autophagy is an essential survival mechanism during energy stress in the heart. Oxidative stress is activated by energy stress, but its role in mediating autophagy is poorly understood. NADPH oxidase (Nox) 4 is an enzyme that generates reactive oxygen species (ROS) at intracellular membranes. Whether Nox4 acts as a sensor of energy stress to mediate activation of autophagy is unknown. OBJECTIVE: We investigated whether Nox4 is involved in the regulation of autophagy and cell survival during energy stress in cardiomyocytes. METHODS AND RESULTS: Production of ROS in cardiomyocytes was increased during glucose deprivation (GD) in a Nox4-dependent manner. Protein levels and the ROS-producing activity of Nox4 were increased in the endoplasmic reticulum (ER), but not in mitochondria, in response to GD. Selective knockdown of Nox4, but not Nox2, or selective reduction of ROS in the ER with ER-targeted catalase, but not mitochondria-targeted perioxiredoxin 3, abrogated GD-induced autophagy. Nox4 promoted autophagy during GD through activation of the protein kinase RNA-activated-like ER kinase pathway by suppression of prolyl hydroxylase 4. The decrease in cell survival during GD in the presence of Nox4 knockdown was rescued by reactivation of autophagy by Atg7 overexpression, indicating that the effect of Nox4 on cell survival is critically mediated through regulation of autophagy. Nox4 was activated during fasting and prolonged ischemia in the mouse heart, where Nox4 is also required for autophagy activation and cardioprotection. CONCLUSIONS: Nox4 critically mediates autophagy in response to energy stress in cardiomyocytes by eliciting ROS in the ER and stimulating the protein kinase RNA-activated-like ER kinase signaling pathway.

The question of whether population density affects the amount of household automobile travel in the United States is revisited. Controls for income and demographics are included in a multivariate regression model of vehicle travel that includes vehicle ownership as an intermediate factor and that treats a household's pick of neighborhood density and the amount of travel as a simultaneous relationship. The data come from the 1990 Nationwide Personal Transportation Survey. It is found that density matters, but not much. A 10 percent increase in density leads to only a 0.7 percent reduction in household automobile travel. By comparison, a 10 percent increase in household income leads to a 3 percent increase in automobile travel. The results are similar when vehicle trips are used as the dependent variable. The effect of density is so small that even a relatively large-scale shift to urban densities would have a negligible impact on total vehicle travel.

OBJECTIVE: I review and critique basic ideas of both traditional error/risk analysis and the newer and contrasting paradigm of resilience engineering. BACKGROUND: Analysis of human error has matured and been applied over the past 50 years by human factors engineers, whereas the resilience engineering paradigm is relatively new. METHOD: Fundamental ideas and examples of human factors applications of each approach are presented and contrasted. RESULTS: Probabilistic risk analysis provides mathematical rigor in generalizing on past error events to identify system vulnerabilities, but prediction is problematical because (a) error definition is arbitrary, and thus it is difficult to infer valid probabilities of human error to input to quantitative models, and (b) future accident conditions are likely to be quite different from those of past accidents. The new resilience engineering paradigm, in contrast, is oriented toward organizational process and is concerned with anticipating, mitigating, and preparing for graceful recovery from future events. CONCLUSION: Resilience engineering complements traditional error analysis but has yet to provide useful quantification and operational methods. APPLICATION: A best safety strategy is to use both approaches.

Consumption of renewable energy in the United States is the highest in history, contributing to energy security, greenhouse gas reductions, and other social, economic, and environmental benefits. The largest single source of renewable energy is biomass, representing 3.9 quadrillion of 9.6 quadrillion British thermal units (Btu) in 2015 (EIA 2016). Biomass includes agricultural and forestry resources, municipal solid waste (MSW), and algae. For more than a decade, the U.S. Department of Energy (DOE) has been quantifying the potential of U.S. biomass resources, under biophysical and economic constraints, for production of renewable energy and bioproducts. The 2016 Billion-Ton Report: Advancing Domestic Resources for a Thriving Bioeconomy (BT16) evaluates the most recent estimates of potential biomass that could be available for new industrial uses in the future. BT16 consists of two volumes: Volume 1 (this volume) focuses on resource analysis—projecting biomass potentially available at specified prices. Volume 2 evaluates changes in environmental sustainability indicators— water quality and quantity, greenhouse gas emissions, air quality, soil organic carbon, and biodiversity—associated with select production scenarios in volume 1. The following is a summary of BT16, volume 1.

Abstract An examination of the variational formulations confirms the similarity between the incompatible displacement model and the assumed stress hybrid model that was pointed out by Irons in 1972. But the basic differences between the two are also identified. For 8‐node solid elements the assumed stress terms obtained through a rational procedure also agree with those deduced by Irons purely from his physical insight.

PURPOSE: Although focused reviews have characterized subsets of the literature on the arts and humanities in medical education, a large-scale overview of the field is needed to inform efforts to strengthen these approaches in medicine. METHOD: The authors conducted a scoping review in 2019 to identify how the arts and humanities are used to educate physicians and interprofessional learners across the medical education continuum in Canada and the United States. A search strategy involving 7 databases identified 21,985 citations. Five reviewers independently screened the titles and abstracts. Full-text screening followed (n = 4,649). Of these, 769 records met the inclusion criteria. The authors performed descriptive and statistical analyses and conducted semistructured interviews with 15 stakeholders. RESULTS: The literature is dominated by conceptual works (n = 294) that critically engaged with arts and humanities approaches or generally called for their use in medical education, followed by program descriptions (n = 255). The literary arts (n = 197) were most common. Less than a third of records explicitly engaged theory as a strong component (n = 230). Of descriptive and empirical records (n = 424), more than half concerned undergraduate medical education (n = 245). There were gaps in the literature on interprofessional education, program evaluation, and learner assessment. Programming was most often taught by medical faculty who published their initiatives (n = 236). Absent were voices of contributing artists, docents, and other arts and humanities practitioners from outside medicine. Stakeholders confirmed that these findings resonated with their experiences. CONCLUSIONS: This literature is characterized by brief, episodic installments, privileging a biomedical orientation and largely lacking a theoretical frame to weave the installments into a larger story that accumulates over time and across subfields. These findings should inform efforts to promote, integrate, and study uses of the arts and humanities in medical education.

The growing amount of waste created by products reaching the end of their useful lives poses challenges for the environment, governments and manufacturers. Processing alternatives include reuse, remanufacturing, recycling, storage and disposal. With disposal considered the least desirable, the first process required by the remaining alternatives is disassembly. Just as the assembly line is considered the most efficient way to assemble a product, the disassembly line is the most efficient way to disassemble a product. Finding the optimal balance for the multi-objective disassembly line balancing problem is computationally intensive due to exponential growth. With exhaustive search calculations quickly becoming prohibitively large, methodologies from the field of combinatorial optimization hold promise for providing solutions. The disassembly line balancing problem is described here, then defined mathematically and proven to belong to the class of unary NP-complete problems. Known optimal instances of the problem are developed, then disassembly line versions of exhaustive search, genetic algorithm and ant colony optimization metaheuristics, a greedy algorithm, and greedy/hill-climbing and greedy/2-optimal hybrid heuristics are presented and compared along with a novel uninformed general-purpose search heuristic.

Abstract Under the Federal Aviation Administration’s (FAA) Aviation Climate Change Research Initiative (ACCRI), non-CO2 climatic impacts of commercial aviation are assessed for current (2006) and for future (2050) baseline and mitigation scenarios. The effects of the non-CO2 aircraft emissions are examined using a number of advanced climate and atmospheric chemistry transport models. Radiative forcing (RF) estimates for individual forcing effects are provided as a range for comparison against those published in the literature. Preliminary results for selected RF components for 2050 scenarios indicate that a 2% increase in fuel efficiency and a decrease in NOx emissions due to advanced aircraft technologies and operational procedures, as well as the introduction of renewable alternative fuels, will significantly decrease future aviation climate impacts. In particular, the use of renewable fuels will further decrease RF associated with sulfate aerosol and black carbon. While this focused ACCRI program effort has yielded significant new knowledge, fundamental uncertainties remain in our understanding of aviation climate impacts. These include several chemical and physical processes associated with NOx–O3–CH4 interactions and the formation of aviation-produced contrails and the effects of aviation soot aerosols on cirrus clouds as well as on deriving a measure of change in temperature from RF for aviation non-CO2 climate impacts—an important metric that informs decision-making.

Abstract Special accurate and efficient hybrid elements were developed to account for notch‐tip singularities of type r γ , where γ can be complex. Proper normalization of the notch‐tip element size was used to minimize the oscillation of the assumed function around the boundaries of the element and to improve the accuracy of the solution. Examples of various notch angles and sizes are presented.

This paper formulates a new approach for improvement of air traffic flow management at airports, which leads to more efficient utilization of existing airport capacity to alleviate the consequences of congestion. A new model is presented, which first considers the runways and arrival and departure fixes jointly as a single system resource, and second considers arrivals and departures simultaneously as two interdependent processes. The model takes into account the interaction between runway capacity and capacities of fixes to optimize the traffic flow through the airport system. The effects are achieved by dynamic time-dependent allocation of airport capacity and flows between arrivals and departures coordinated with the operational constraints at runways and arrival and departure fixes as well as with dynamics of traffic demand and weather. Numerical examples illustrate the potential benefits of the approach.

Cooperative strategies of individuals within a distributed organization can contribute to increased efficiency of operations and safety. We examine these processes in the context of a particular work domain: railroad operations. Analyses revealed a variety of informal cooperative strategies that railroad workers have developed that span across multiple railroad crafts including roadway workers, train crews, and railroad dispatchers. These informal, proactive communications foster shared situation awareness across the distributed organization, facilitate work, and contribute to the overall efficiency, safety, and resilience to error of railroad operations. We discuss design implications for leveraging new digital technologies and location-finding systems to more effectively support these informal strategies, enhance shared situation awareness, and promote high reliability performance.

This paper describes a bicriterion equilibrium traffic assignment model that accurately forecasts path choices and consequent total arc flows for a stochastically diverse set of trips. Called T2, its develops around a linear generalized cost model, which generalizes classical traffic assignment by relaxing the value-of-time parameter from a constant to a random variable with an arbitrary probability distribution. For the case where arc time and/or cost are flow dependent, this paper formulates conditions and algorithms for stochastic bicriterion user-optimal equilibrium arc flows, which reflect every trip's exclusive use of a path that minimizes its particular perception of generalized cost.

The pressure distribution in the contact zones and the radii at which flat and smooth axisymmetric, linear elastic plates will separate were computed for several thicknesses as a function of the configuration of the bolt load by the finite element method. The radii of separation were also measured by two experimental methods. One method employed autoradiographic techniques. The other method measured the polished area around the bolt hole of the plates caused by sliding under load in the contact zone. The computational and experimental results are in agreement and these yield smaller zones of contact than indicated by the literature. It is shown that the discrepancy is due to an assumption made in the previous analyses.

Today, about one-fourth of U.S. commercial service airports, including 41 of the busiest 50, are either in nonattainment or maintenance areas per the National Ambient Air Quality Standards. U.S. aviation activity is forecasted to triple by 2025, while at the same time, the U.S. Environmental Protection Agency (EPA) is evaluating stricter particulate matter (PM) standards on the basis of documented human health and welfare impacts. Stricter federal standards are expected to impede capacity and limit aviation growth if regulatory mandated emission reductions occur as for other non-aviation sources (i.e., automobiles, power plants, etc.). In addition, strong interest exists as to the role aviation emissions play in air quality and climate change issues. These reasons underpin the need to quantify and understand PM emissions from certified commercial aircraft engines, which has led to the need for a methodology to predict these emissions. Standardized sampling techniques to measure volatile and nonvolatile PM emissions from aircraft engines do not exist. As such, a first-order approximation (FOA) was derived to fill this need based on available information. FOA1.0 only allowed prediction of nonvolatile PM. FOA2.0 was a change to include volatile PM emissions on the basis of the ratio of nonvolatile to volatile emissions. Recent collaborative efforts by industry (manufacturers and airlines), research establishments, and regulators have begun to provide further insight into the estimation of the PM emissions. The resultant PM measurement datasets are being analyzed to refine sampling techniques and progress towards standardized PM measurements. These preliminary measurement datasets also support the continued refinement of the FOA methodology. FOA3.0 disaggregated the prediction techniques to allow for independent prediction of nonvolatile and volatile emissions on a more theoretical basis. The Committee for Aviation Environmental Protection of the International Civil Aviation Organization endorsed the use of FOA3.0 in February 2007. Further commitment was made to improve the FOA as new data become available, until such time the methodology is rendered obsolete by a fully validated database of PM emission indices for today's certified commercial fleet. This paper discusses related assumptions and derived equations for the FOA3.0 methodology used worldwide to estimate PM emissions from certified commercial aircraft engines within the vicinity of airports.