Cell phone conversing while driving in New Zealand: prevalence, risk perception and legislation.

PubMed

Hallett, Charlene; Lambert, Anthony; Regan, Michael A

2011-05-01

This study investigated (i) the prevalence of conversing on a cell phone while driving in New Zealand, (ii) respondents' perception of risk regarding this behaviour and (iii) attitudes towards legislation banning cell phone use while driving. In addition, the study examined the association between the prevalence of conversing on a cell phone and risk perception. Anonymous, self-reported, survey data was collected via the internet from 1057 drivers nationwide regarding the frequency of conversing on a cell phone, including hands-free and hand-held conversing, risk perception, views on legislation, and demographic information. A positive relationship was found between the frequency of conversing on a cell phone and risk perception; that is, as the frequency of conversing on a cell phone increased, the perceived risk of this behaviour decreased. Copyright © 2010 Elsevier Ltd. All rights reserved.

Solar Spectrum Photocatalytic Conversion of CO2 and Water Vapor Into Hydrocarbons Using TiO2 Nanoparticle Membranes

NASA Astrophysics Data System (ADS)

Rani, Sanju; Bao, Ningzhong; Roy, Somnath C.

2014-01-01

A viable option for recycling carbon dioxide is through the sunlight-powered photocatalytic conversion of CO2 and water vapor into hydrocarbon fuels over highly active nanocatalysts. With photocatalytic CO2 reduction sunlight, a renewable energy source as durable as the sun, is used to drive the catalytic reaction with the resultant fuel products compatible with the current hydrocarbon-based energy infrastructure. The use of co-catalyst (Cu, Pt)-sensitized TiO2 nanoparticle wafers in the photocatalytic conversion of CO2 and water vapor to hydrocarbon fuels, with optimal humidity levels and exposure times established. We also attempted to increase product formation by sputtering both co-catalysts on the nanoparticle wafer's surface, with the resulting product rates significantly higher than that of either the Cu or Pt coated samples. When the TiO2 nanoparticle wafers are used in a flow-through membrane implementation we find a significant increase in product rates of formation, including methane, hydrogen, and carbon monoxide. We believe that nanocatalyst-based flow-through membranes are a viable route for achieving large-scale and low cost photocatalytic solar fuel production.

Driving performance while using cell phones: an observational study.

PubMed

Rosenbloom, Tova

2006-01-01

Through spontaneous driving observations, this study sought to examine the impact of using a hands-free cell phone while driving on speed and safe gap keeping behaviors. The study also examined the association between the measure of disturbance created by using a cell phone and the driver's awareness of the disturbance. Twenty-three male adults were observed while driving for an hour and a half each; drivers were unaware of being observed. During the session, each of the participants received a phone call, initiated by an associate of the observer. The experiment was divided into two periods during which the experimental parameters were monitored: 10 minutes during conversation on a cell phone and 10 minutes of non-conversation on a hands-free cell phone. After the experiment, the driver was questioned concerning the extent to which his/her driving was disturbed by the cell phone conversation. T-test for matched samples revealed that the gaps between the drivers' cars and those in front of them diminished when drivers were engaged in the cell phone conversations. Repeated measures ANOVA revealed that drivers that had short conversations did not change their speed, while drivers who were engaged in long (over 16 minutes) conversations drove faster. No effect of drivers' awareness toward cell phone-related disturbance on actual driving behavior monitored in the present study was found.

Impact of mobile phone use on car-following behaviour of young drivers.

PubMed

Saifuzzaman, Mohammad; Haque, Md Mazharul; Zheng, Zuduo; Washington, Simon

2015-09-01

Multitasking, such as the concurrent use of a mobile phone and operating a motor vehicle, is a significant distraction that impairs driving performance and is becoming a leading cause of motor vehicle crashes. This study investigates the impact of mobile phone conversations on car-following behaviour. The CARRS-Q Advanced Driving Simulator was used to test a group of young Australian drivers aged 18-26 years on a car-following task in three randomised phone conditions: baseline (no phone conversation), hands-free and handheld. Repeated measure ANOVA was applied to examine the effect of mobile phone distraction on selected car-following variables such as driving speed, spacing, and time headway. Overall, drivers tended to select slower driving speeds, larger vehicle spacings, and longer time headways when they were engaged in either hands-free or handheld phone conversations, suggesting possible risk compensatory behaviour. In addition, phone conversations while driving influenced car-following behaviour such that variability was increased in driving speeds, vehicle spacings, and acceleration and decelerations. To further investigate car-following behaviour of distracted drivers, driver time headways were modelled using Generalized Estimation Equation (GEE). After controlling for various exogenous factors, the model predicts an increase of 0.33s in time headway when a driver is engaged in hands-free phone conversation and a 0.75s increase for handheld phone conversation. The findings will improve the collective understanding of distraction on driving performance, in particular car following behaviour which is most critical in the determination of rear-end crashes. Copyright © 2015 Elsevier Ltd. All rights reserved.

Impute DC link (IDCL) cell based power converters and control thereof

DOEpatents

Divan, Deepakraj M.; Prasai, Anish; Hernendez, Jorge; Moghe, Rohit; Iyer, Amrit; Kandula, Rajendra Prasad

2016-04-26

Power flow controllers based on Imputed DC Link (IDCL) cells are provided. The IDCL cell is a self-contained power electronic building block (PEBB). The IDCL cell may be stacked in series and parallel to achieve power flow control at higher voltage and current levels. Each IDCL cell may comprise a gate drive, a voltage sharing module, and a thermal management component in order to facilitate easy integration of the cell into a variety of applications. By providing direct AC conversion, the IDCL cell based AC/AC converters reduce device count, eliminate the use of electrolytic capacitors that have life and reliability issues, and improve system efficiency compared with similarly rated back-to-back inverter system.

Parent comments and instruction during the first four months of supervised driving: an opportunity missed?

PubMed

Goodwin, Arthur H; Foss, Robert D; Margolis, Lewis H; Harrell, Stephanie

2014-08-01

The present study examined the nature of the comments and instruction provided by parents during supervised driving. Unlike previous studies which rely on self-report, the data in this study were obtained through direct observation of parents and teens using in-vehicle cameras with audio recording. The cameras were installed in the vehicles of 50 families for the first four months of the learner license stage. The findings show a great deal of conversation takes place while teens are driving with a supervisor, and that much of this conversation concerns driving. Sixty-one percent (61%) of all recorded clips included driving-related conversation. The most common type of comment by parents was instruction about vehicle handling or operation, observed in 53% of those clips with conversation about driving. This was followed by pointing out something about the driving environment (such as when it was clear to enter traffic; 23%), negative comments about the teen's driving (22%), and helping the driver navigate (18%). Other potentially helpful types of instruction, including explanation or insights regarding higher order skills (e.g., hazard anticipation and detection), were noticeably less frequent. Moreover, higher order instruction remained low during the first four months of the learner stage, even as instruction about vehicle handling/operation decreased. These findings suggest parents are not taking full advantage of the opportunity provided by mandatory periods of supervised driving to help their children develop an understanding of important aspects of driving. Copyright © 2014 Elsevier Ltd. All rights reserved.

Technologies, Multitasking, and Driving: Attending to and Preparing for a Mobile Phone Conversation in a Car

ERIC Educational Resources Information Center

Haddington, Pentti; Rauniomaa, Mirka

2011-01-01

This article investigates mobile phone calls initiated or received by drivers and passengers in cars and focuses on the participants' actions before the telephone conversation proper. Drawing on video-recorded data of real driving situations, and building on conversation analysis and multimodal interaction analysis, this article discusses how…

Hydraulic and Mechanical Effects from Gas Hydrate Conversion and Secondary Gas Hydrate Formation during Injection of CO2 into CH4-Hydrate-Bearing Sediments

NASA Astrophysics Data System (ADS)

Bigalke, N.; Deusner, C.; Kossel, E.; Schicks, J. M.; Spangenberg, E.; Priegnitz, M.; Heeschen, K. U.; Abendroth, S.; Thaler, J.; Haeckel, M.

2014-12-01

The injection of CO2 into CH4-hydrate-bearing sediments has the potential to drive natural gas production and simultaneously sequester CO2 by hydrate conversion. The process aims at maintaining the in situ hydrate saturation and structure and causing limited impact on soil hydraulic properties and geomechanical stability. However, to increase hydrate conversion yields and rates it must potentially be assisted by thermal stimulation or depressurization. Further, secondary formation of CO2-rich hydrates from pore water and injected CO2 enhances hydrate conversion and CH4 production yields [1]. Technical stimulation and secondary hydrate formation add significant complexity to the bulk conversion process resulting in spatial and temporal effects on hydraulic and geomechanical properties that cannot be predicted by current reservoir simulation codes. In a combined experimental and numerical approach, it is our objective to elucidate both hydraulic and mechanical effects of CO2 injection and CH4-CO2-hydrate conversion in CH4-hydrate bearing soils. For the experimental approach we used various high-pressure flow-through systems equipped with different online and in situ monitoring tools (e.g. Raman microscopy, MRI and ERT). One particular focus was the design of triaxial cell experimental systems, which enable us to study sample behavior even during large deformations and particle flow. We present results from various flow-through high-pressure experimental studies on different scales, which indicate that hydraulic and geomechanical properties of hydrate-bearing sediments are drastically altered during and after injection of CO2. We discuss the results in light of the competing processes of hydrate dissociation, hydrate conversion and secondary hydrate formation. Our results will also contribute to the understanding of effects of temperature and pressure changes leading to dissociation of gas hydrates in ocean and permafrost systems. [1] Deusner C, Bigalke N, Kossel E, Haeckel M. Methane Production from Gas Hydrate Deposits through Injection of Supercritical CO2. Energies 2012:5(7): 2112-2140.

A current drive by using the fast wave in frequency range higher than two timeslower hybrid resonance frequency on tokamaks

NASA Astrophysics Data System (ADS)

Kim, Sun Ho; Hwang, Yong Seok; Jeong, Seung Ho; Wang, Son Jong; Kwak, Jong Gu

2017-10-01

An efficient current drive scheme in central or off-axis region is required for the steady state operation of tokamak fusion reactors. The current drive by using the fast wave in frequency range higher than two times lower hybrid resonance (w>2wlh) could be such a scheme in high density, high temperature reactor-grade tokamak plasmas. First, it has relatively higher parallel electric field to the magnetic field favorable to the current generation, compared to fast waves in other frequency range. Second, it can deeply penetrate into high density plasmas compared to the slow wave in the same frequency range. Third, parasitic coupling to the slow wave can contribute also to the current drive avoiding parametric instability, thermal mode conversion and ion heating occured in the frequency range w<2wlh. In this study, the propagation boundary, accessibility, and the energy flow of the fast wave are given via cold dispersion relation and group velocity. The power absorption and current drive efficiency are discussed qualitatively through the hot dispersion relation and the polarization. Finally, those characteristics are confirmed with ray tracing code GENRAY for the KSTAR plasmas.

Does Talking on a Cell Phone, With a Passenger, or Dialing Affect Driving Performance? An Updated Systematic Review and Meta-Analysis of Experimental Studies.

PubMed

Caird, Jeff K; Simmons, Sarah M; Wiley, Katelyn; Johnston, Kate A; Horrey, William J

2018-02-01

Objective An up-to-date meta-analysis of experimental research on talking and driving is needed to provide a comprehensive, empirical, and credible basis for policy, legislation, countermeasures, and future research. Background The effects of cell, mobile, and smart phone use on driving safety continues to be a contentious societal issue. Method All available studies that measured the effects of cell phone use on driving were identified through a variety of search methods and databases. A total of 93 studies containing 106 experiments met the inclusion criteria. Coded independent variables included conversation target (handheld, hands-free, and passenger), setting (laboratory, simulation, or on road), and conversation type (natural, cognitive task, and dialing). Coded dependent variables included reaction time, stimulus detection, lane positioning, speed, headway, eye movements, and collisions. Results The overall sample had 4,382 participants, with driver ages ranging from 14 to 84 years ( M = 25.5, SD = 5.2). Conversation on a handheld or hands-free phone resulted in performance costs when compared with baseline driving for reaction time, stimulus detection, and collisions. Passenger conversation had a similar pattern of effect sizes. Dialing while driving had large performance costs for many variables. Conclusion This meta-analysis found that cell phone and passenger conversation produced moderate performance costs. Drivers minimally compensated while conversing on a cell phone by increasing headway or reducing speed. A number of additional meta-analytic questions are discussed. Application The results can be used to guide legislation, policy, countermeasures, and future research.

Effects of road infrastructure and traffic complexity in speed adaptation behaviour of distracted drivers.

PubMed

Oviedo-Trespalacios, Oscar; Haque, Md Mazharul; King, Mark; Washington, Simon

2017-04-01

The use of mobile phones while driving remains a major human factors issue in the transport system. A significant safety concern is that driving while distracted by a mobile phone potentially modifies the driving speed leading to conflicts with other road users and consequently increases crash risk. However, the lack of systematic knowledge of the mechanisms involved in speed adaptation of distracted drivers constrains the explanation and modelling of the extent of this phenomenon. The objective of this study was to investigate speed adaptation of distracted drivers under varying road infrastructure and traffic complexity conditions. The CARRS-Q Advanced Driving Simulator was used to test participants on a simulated road with different traffic conditions, such as free flow traffic along straight roads, driving in urbanized areas, and driving in heavy traffic along suburban roads. Thirty-two licensed young drivers drove the simulator under three phone conditions: baseline (no phone conversation), hands-free and handheld phone conversations. To understand the relationships between distraction, road infrastructure and traffic complexity, speed adaptation calculated as the deviation of driving speed from the posted speed limit was modelled using a decision tree. The identified groups of road infrastructure and traffic characteristics from the decision tree were then modelled with a Generalized Linear Mixed Model (GLMM) with repeated measures to develop inferences about speed adaptation behaviour of distracted drivers. The GLMM also included driver characteristics and secondary task demands as predictors of speed adaptation. Results indicated that complex road environments like urbanization, car-following situations along suburban roads, and curved road alignment significantly influenced speed adaptation behaviour. Distracted drivers selected a lower speed while driving along a curved road or during car-following situations, but speed adaptation was negligible in the presence of high visual cutter, indicating the prioritization of the driving task over the secondary task. Additionally, drivers who scored high on self-reported safe attitudes towards mobile phone usage, and who reported prior involvement in a road traffic crash, selected a lower driving speed in the distracted condition than in the baseline. The results aid in understanding how driving task demands influence speed adaptation of distracted drivers under various road infrastructure and traffic complexity conditions. Copyright © 2017 Elsevier Ltd. All rights reserved.

ICRF fast wave current drive and mode conversion current drive in EAST tokamak

NASA Astrophysics Data System (ADS)

Yin, L.; Yang, C.; Gong, X. Y.; Lu, X. Q.; Du, D.; Chen, Y.

2017-10-01

Fast wave in the ion-cyclotron resonance frequency (ICRF) range is a promising candidate for non-inductive current drive (CD), which is essential for long pulse and high performance operation of tokamaks. A numerical study on the ICRF fast wave current drive (FWCD) and mode-conversion current drive (MCCD) in the Experimental Advanced Superconducting Tokamak (EAST) is carried out by means of the coupled full wave and Ehst-Karney parameterization methods. The results show that FWCD efficiency is notable in two frequency regimes, i.e., f ≥ 85 MHz and f = 50-65 MHz, where ion cyclotron absorption is effectively avoided, and the maximum on-axis driven current per unit power can reach 120 kA/MW. The sensitivity of the CD efficiency to the minority ion concentration is confirmed, owing to fast wave mode conversion, and the peak MCCD efficiency is reached for 22% minority-ion concentration. The effects of the wave-launch position and the toroidal wavenumber on the efficiency of current drive are also investigated.

Buoyant production and consumption of turbulence kinetic energy in cloud-topped mixed layers

NASA Technical Reports Server (NTRS)

Randall, D. A.

1984-01-01

It is pointed out that studies of the entraining planetary boundary layer (PBL) have generally emphasized the role of buoyancy fluxes in driving entrainment. The buoyancy flux is proportional to the rate of conversion of the potential energy of the mean flow into the kinetic energy of the turbulence. It is not unusual for conversion to proceed in both directions simultaneously. This occurs, for instance, in both clear and cloudy convective mixed layers which are capped by inversions. A partitioning of the net conversion into positive parts, generating turbulence kinetic energy (TKE), and negative parts (TKE-consuming), would make it possible to include the positive part in the gross production rate, and closure would be achieved. Three different approaches to partitioning have been proposed. The present investigation is concerned with a comparison of the three partitioning theories. Particular attention is given to the cloud-topped mixed layer because in this case the differences between two partitioning approaches are most apparent.

Ensembles of 21st Century Colorado River Flow Projections Exhibit Substantial Diversity in Response to Seasonal Hydroclimatic Scenarios

NASA Astrophysics Data System (ADS)

McAfee, S. A.; Woodhouse, C. A.; McCabe, G. J., Jr.; Pederson, G. T.

2016-12-01

Approximately 40 million people depend on the Colorado River, and that number is likely to grow in the future, making the River's response to projected increases in temperature and possible changes in precipitation a critical societal issue. By far the most common way of approaching the problem is synthesize results obtained by forcing a hydrological model with a set of downscaled future climate scenarios. One weakness with this type of analysis is that full hydrologic model simulations can be computationally demanding, and so the number of potential climate futures is generally somewhat limited. Here we sidestep that issue by using a very large set of synthetic climate futures to drive a simple statistical model of water year flow at Lees Ferry. 62,500 climate series, comprising 500 iterations of 125 unique combinations of summer temperature changes ranging from 0 to +4°C and summer and winter precipitation changes ranging from -20 to +20% were input into the flow model. Without substantial temperature increases, significant increases in the occurrence of very low flows (<75%) were unlikely, even with sharp decreases in temperature. Conversely, increases in precipitation, could buffer the effect of summer temperature increases up to about 3°C on mean water year flows. While very simple models like this one are inappropriate for some questions, they do provide an effective way of prioritizing and framing more complex investigations, and facilitate conversations with stakeholders about research directions.

Impact of distraction on the driving performance of adolescents with and without attention-deficit/hyperactivity disorder.

PubMed

Narad, Megan; Garner, Annie A; Brassell, Anne A; Saxby, Dyani; Antonini, Tanya N; O'Brien, Kathleen M; Tamm, Leanne; Matthews, Gerald; Epstein, Jeffery N

2013-10-01

This study extends the literature regarding attention-deficit/hyperactivity disorder (ADHD)-related driving impairments to a newly licensed, adolescent population. To investigate the combined risks of adolescence, ADHD, and distracted driving (cell phone conversation and text messaging) on driving performance. Adolescents aged 16 to 17 years with (n = 28) and without (n = 33) ADHD engaged in a simulated drive under 3 conditions (no distraction, cell phone conversation, and texting). During each condition, one unexpected event (eg, another car suddenly merging into driver's lane) was introduced. Cell phone conversation, texting, and no distraction while driving. Self-report of driving history, average speed, standard deviation of speed, standard deviation of lateral position, and braking reaction time during driving simulation. Adolescents with ADHD reported fewer months of driving experience and a higher proportion of driving violations than control subjects. After controlling for months of driving history, adolescents with ADHD demonstrated more variability in speed and lane position than control subjects. There were no group differences for braking reaction time. Furthermore, texting negatively impacted the driving performance of all participants as evidenced by increased variability in speed and lane position. To our knowledge, this study is one of the first to investigate distracted driving in adolescents with ADHD and adds to a growing body of literature documenting that individuals with ADHD are at increased risk for negative driving outcomes. Furthermore, texting significantly impairs the driving performance of all adolescents and increases existing driving-related impairment in adolescents with ADHD, highlighting the need for education and enforcement of regulations against texting for this age group.

Conversation Effects on Neural Mechanisms Underlying Reaction Time to Visual Events while Viewing a Driving Scene using MEG

PubMed Central

Bowyer, Susan M.; Hsieh, Li; Moran, John E.; Young, Richard A.; Manoharan, Arun; Liao, Chia-cheng Jason; Malladi, Kiran; Yu, Ya-Ju; Chiang, Yow-Ren; Tepley, Norman

2009-01-01

Magnetoencephalography (MEG) imaging examined the neural mechanisms that modulate reaction times to visual events while viewing a driving video, with and without a conversation. Twenty-four subjects ages 18–65 were monitored by whole-head MEG. The primary tasks were to monitor a driving video and to depress a foot pedal in response to a small red light presented to the left or below the driving scene at unpredictable times. The behavioral reaction time (RT) to the lights was recorded. The secondary task was a hands-free conversation. The subject pressed a button to answer a ring tone, and then covertly answered pre-recorded non-emotional questions such as “What is your birth date?” RTs for the conversation task (1043ms, SE=65ms) were slightly longer than for the primary task (baseline no conversation (944ms, SE=48ms). During the primary task RTs were inversely related to the amount of brain activity detected by MEG in the right superior parietal lobe (Brodmann’s Area 7). Brain activity was seen in the 200 to 300 ms range after the onset of the red light and in the visual cortex (BA 19) about 85 ms after the red light. Conversation reduced the strengths of these regression relationships and increased mean RT. Conversation may contribute to increased reaction times by (1) damping brain activation in specific regions during specific time windows, or (2) reducing facilitation from attention inputs into those areas. These laboratory findings should not be interpreted as indicative of real-world driving, without on-road validation, and comparison to other in-vehicle tasks. PMID:18992728

Oxygen delivery, consumption, and conversion to reactive oxygen species in experimental models of diabetic retinopathy

PubMed Central

Eshaq, Randa S.; Wright, William S.; Harris, Norman R.

2014-01-01

Retinal tissue receives its supply of oxygen from two sources – the retinal and choroidal circulations. Decreases in retinal blood flow occur in the early stages of diabetes, with the eventual development of hypoxia thought to contribute to pathological neovascularization. Oxygen consumption in the retina has been found to decrease in diabetes, possibly due to either a reduction in neuronal metabolism or to cell death. Diabetes also enhances the rate of conversion of oxygen to superoxide in the retina, with experimental evidence suggesting that mitochondrial superoxide not only drives the overall production of reactive oxygen species, but also initiates several pathways leading to retinopathy, including the increased activity of the polyol and hexosamine pathways, increased production of advanced glycation end products and expression of their receptors, and activation of protein kinase C. PMID:24936440

Oxygen delivery, consumption, and conversion to reactive oxygen species in experimental models of diabetic retinopathy.

PubMed

Eshaq, Randa S; Wright, William S; Harris, Norman R

2014-01-01

Retinal tissue receives its supply of oxygen from two sources - the retinal and choroidal circulations. Decreases in retinal blood flow occur in the early stages of diabetes, with the eventual development of hypoxia thought to contribute to pathological neovascularization. Oxygen consumption in the retina has been found to decrease in diabetes, possibly due to either a reduction in neuronal metabolism or to cell death. Diabetes also enhances the rate of conversion of oxygen to superoxide in the retina, with experimental evidence suggesting that mitochondrial superoxide not only drives the overall production of reactive oxygen species, but also initiates several pathways leading to retinopathy, including the increased activity of the polyol and hexosamine pathways, increased production of advanced glycation end products and expression of their receptors, and activation of protein kinase C.

Providing views of the driving scene to drivers' conversation partners mitigates cell-phone-related distraction.

PubMed

Gaspar, John G; Street, Whitney N; Windsor, Matthew B; Carbonari, Ronald; Kaczmarski, Henry; Kramer, Arthur F; Mathewson, Kyle E

2014-12-01

Cell-phone use impairs driving safety and performance. This impairment may stem from the remote partner's lack of awareness about the driving situation. In this study, pairs of participants completed a driving simulator task while conversing naturally in the car and while talking on a hands-free cell phone. In a third condition, the driver drove while the remote conversation partner could see video of both the road ahead and the driver's face. We tested the extent to which this additional visual information diminished the negative effects of cell-phone distraction and increased situational awareness. Collision rates for unexpected merging events were high when participants drove in a cell-phone condition but were reduced when they were in a videophone condition, reaching a level equal to that observed when they drove with an in-car passenger or drove alone. Drivers and their partners made shorter utterances and made longer, more frequent traffic references when they spoke in the videophone rather than the cell-phone condition. Providing a view of the driving scene allows remote partners to help drivers by modulating their conversation and referring to traffic more often. © The Author(s) 2014.

The Impact of Distraction on the Driving Performance of Adolescents with and without Attention Deficit Hyperactivity Disorder

PubMed Central

Narad, Megan; Garner, Annie A.; Brassell, Anne A.; Saxby, Dyani; Antonini, Tanya N.; O'Brien, Kathleen M.; Tamm, Leanne; Matthews, Gerald; Epstein, Jeffery N.

2013-01-01

Importance This study extends the literature regarding Attention-Deficit/Hyperactivity Disorder (ADHD) related driving impairments to a newly-licensed, adolescent population. Objective To investigate the combined risks of adolescence, ADHD, and distracted driving (cell phone conversation and text messaging) on driving performance. Design Adolescents with and without ADHD engaged in a simulated drive under three conditions (no distraction, cell phone conversation, texting). During each condition, one unexpected event (e.g., car suddenly merging into driver's lane) was introduced. Setting Driving simulator. Participants Adolescents aged 16–17 with ADHD (n=28) and controls (n=33). Interventions/Main Exposures Cell phone conversation, texting, and no distraction while driving. Outcome Measures Self-report of driving history; Average speed, standard deviation of speed, standard deviation of lateral position, braking reaction time during driving simulation. Results Adolescents with ADHD reported fewer months of driving experience and a higher proportion of driving violations than controls. After controlling for months of driving history, adolescents with ADHD demonstrated more variability in speed and lane position than controls. There were no group differences for braking reaction time. Further, texting negatively impacted the driving performance of all participants as evidenced by increased variability in speed and lane position. Conclusions This study, one of the first to investigate distracted driving in adolescents with ADHD, adds to a growing body of literature documenting that individuals with ADHD are at increased risk for negative driving outcomes. Furthermore, texting significantly impairs the driving performance of all adolescents and increases existing driving-related impairment in adolescents with ADHD, highlighting the need for education and enforcement of regulations against texting for this age group. PMID:23939758

Continuous Flow Polymer Synthesis toward Reproducible Large-Scale Production for Efficient Bulk Heterojunction Organic Solar Cells.

PubMed

Pirotte, Geert; Kesters, Jurgen; Verstappen, Pieter; Govaerts, Sanne; Manca, Jean; Lutsen, Laurence; Vanderzande, Dirk; Maes, Wouter

2015-10-12

Organic photovoltaics (OPV) have attracted great interest as a solar cell technology with appealing mechanical, aesthetical, and economies-of-scale features. To drive OPV toward economic viability, low-cost, large-scale module production has to be realized in combination with increased top-quality material availability and minimal batch-to-batch variation. To this extent, continuous flow chemistry can serve as a powerful tool. In this contribution, a flow protocol is optimized for the high performance benzodithiophene-thienopyrroledione copolymer PBDTTPD and the material quality is probed through systematic solar-cell evaluation. A stepwise approach is adopted to turn the batch process into a reproducible and scalable continuous flow procedure. Solar cell devices fabricated using the obtained polymer batches deliver an average power conversion efficiency of 7.2 %. Upon incorporation of an ionic polythiophene-based cathodic interlayer, the photovoltaic performance could be enhanced to a maximum efficiency of 9.1 %. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Land use change and its driving forces toward mutual conversion in Zhangjiakou City, a farming-pastoral ecotone in Northern China.

PubMed

Liu, Chao; Xu, Yueqing; Sun, Piling; Huang, An; Zheng, Weiran

2017-09-14

Land use/cover change (LUCC), a local environmental issue of global importance, and its driving forces have been crucial issues in geography and environmental research. Previous studies primarily focused on major driving factors in various land use types, with few explorations of differences between driving forces of mutual land use type conversions, especially in fragile eco-environments. In this study, Zhangjiakou City, in a farming-pastoral ecotone in Northern China, was taken as an example to analyze land use change between 1989 and 2015, and explore the driving forces of mutual land use type conversions using canonical correlation analysis. Satellite images and government statistics, including social-economic and natural data, were used as sources. Arable land, forestland, and grassland formed the main land use structure. From 1989 to 2015 forestland, orchard land, and construction land significantly increased, while arable land, grassland, unused land, and water areas decreased. Conversions from grassland to forestland; from arable land to orchard land, forestland and construction land; and from unused land to grassland and forestland were the primary land use changes. Among these, the conversion from grassland to forestland had the highest ranking. Average annual precipitation and per capita net income of rural residents positively affected the conversion of arable land to forestland and unused land to grassland. GDP, total population, and urbanization rate contributed most significantly to converting arable land to construction land; total retail sales of social consumer goods, average annual temperature, and GDP had important positive influences in converting arable land to orchard land.

The natural flow regime of Hawaíi streams

NASA Astrophysics Data System (ADS)

Tsang, Y. P.; Strauch, A. M.; Clilverd, H. M.

2016-12-01

Freshwater is a critical, but limited natural resource on tropical islands; sustaining agriculture, industry, hydropower, urban development, and domestic water supply. The hydrology of Hawaíi islands is largely influenced by the health of mountain forests, which capture and absorb rain and fog drip, recharging aquifers and sustaining stream flow. Forests in Hawaíi are being degraded through the replacement of native vegetation with introduced species or conversion to another land use. Streams in the tropics frequently experience flash flooding due to extreme rainfall-runoff events and low flows due to seasonal drought. These patterns drive habitat availability for freshwater fauna, as well as sediment and nutrient export to near-shore ecosystems. Flow regimes can be used to characterize the frequency and magnitude of extreme high and low flows and are influenced by watershed climate, geology, land cover and soil composition. We examined the effect of climate extremes on stream flow from Hawaiian forests using historical flow data to characterize the spatial and temporal patterns in surface water resources. By defining flow regimes from forests we can improve our understanding of climate extremes on water resource availability across tropical island landscapes.

Exergetic analysis of a thermo-generator for automotive application: A dynamic numerical approach

NASA Astrophysics Data System (ADS)

Glavatskaya, O.; Goupil, C.; Bakkali, A. El; Shonda, O.

2012-06-01

It is well known that, when using a passenger car with an ICE (Internal Combustion Engine), only a fraction of the burnt fuel energy actually contributes to drive the vehicle. Typical passenger vehicle engines run about 25% efficiency while a great part of the remaining energy (about 40%), is lost through the exhaust gases. This latter has a significant energy conversion potential since the temperature (more than 300°C) and the mass flow rate are high enough. Thus, direct conversion of heat into electricity is a credible option if the overall system is optimized. This point is crucial since the heat conversion into work process is very sensible to any mismatching of the different parts of the system, and very sensible significant to the possible varying working conditions. All these effects constitute irreversibility sources that degrade the overall efficiency. The exergetic analysis is known to be an efficient tool for finding the root causes of theses irreversible processes. In order to investigate the performance of our automotive thermo-generator we propose an analysis of the exergy flow through the system under dynamic conditions. Taking into account the different irreversible sources such as thermal conduction and Joule effect, we are able to localize and quantify the exergy losses. Then, in order to optimize the thermoelectric converter for a given vehicle, correct actions in term of design and working conditions can be proposed.

The driving forces of land change in the Northern Piedmont of the United States

USGS Publications Warehouse

Auch, Roger F.; Napton, Darrell E.; Kambly, Steven; Moreland, Thomas R.; Sayler, Kristi L.

2012-01-01

Driving forces facilitate or inhibit land-use/land-cover change. Human driving forces include political, economic, cultural, and social attributes that often change across time and space. Remotely sensed imagery provides regional land-change data for the Northern Piedmont, an ecoregion of the United States that continued to urbanize after 1970 through conversion of agricultural and forest land covers to developed uses. Eight major driving forces facilitated most of the land conversion; other drivers inhibited or slowed change. A synergistic web of drivers may be more important in understanding land change than individual drivers by themselves.

A microfluidic fuel cell with flow-through porous electrodes.

PubMed

Kjeang, Erik; Michel, Raphaelle; Harrington, David A; Djilali, Ned; Sinton, David

2008-03-26

A microfluidic fuel cell architecture incorporating flow-through porous electrodes is demonstrated. The design is based on cross-flow of aqueous vanadium redox species through the electrodes into an orthogonally arranged co-laminar exit channel, where the waste solutions provide ionic charge transfer in a membraneless configuration. This flow-through architecture enables improved utilization of the three-dimensional active area inside the porous electrodes and provides enhanced rates of convective/diffusive transport without increasing the parasitic loss required to drive the flow. Prototype fuel cells are fabricated by rapid prototyping with total material cost estimated at 2 USD/unit. Improved performance as compared to previous microfluidic fuel cells is demonstrated, including power densities at room temperature up to 131 mW cm-2. In addition, high overall energy conversion efficiency is obtained through a combination of relatively high levels of fuel utilization and cell voltage. When operated at 1 microL min-1 flow rate, the fuel cell produced 20 mW cm-2 at 0.8 V combined with an active fuel utilization of 94%. Finally, we demonstrate in situ fuel and oxidant regeneration by running the flow-through architecture fuel cell in reverse.

Driven to distraction: dual-Task studies of simulated driving and conversing on a cellular telephone.

PubMed

Strayer, D L; Johnston, W A

2001-11-01

Dual-task studies assessed the effects of cellular-phone conversations on performance of a simulated driving task. Performance was not disrupted by listening to radio broadcasts or listening to a book on tape. Nor was it disrupted by a continuous shadowing task using a handheld phone, ruling out, in this case, dual-task interpretations associated with holding the phone, listening, or speaking, However significant interference was observed in a word-generation variant of the shadowing task, and this deficit increased with the difficulty of driving. Moreover unconstrained conversations using either a handheld or a hands-free cell phone resulted in a twofold increase in the failure to detect simulated traffic signals and slower reactions to those signals that were detected. We suggest that cellular-phone use disrupts performance by diverting attention to an engaging cognitive context other than the one immediately associated with driving.

LETTER: Investigation of the effect of Alfven resonance mode conversion on fast wave current drive in ITER

NASA Astrophysics Data System (ADS)

Alava, M. J.; Heikkinen, J. A.; Hellsten, T.

1995-07-01

In order to reduce or to avoid ion cyclotron damping, the use of frequencies below the ion cyclotron frequency of minority ion species or the second harmonic of majority ion species has been proposed for fast wave current drive based on direct electron absorption. For these scenarios, the Alfven or ion-ion hybrid resonance can appear on the high field side of a tokamak. The presence of these resonances causes parasitic absorption, competing with the electron Landau damping and transit time magnetic pumping responsible for the fast wave current drive. In the present study, neglecting effects from toroidicity, the mode conversion at the Alfven resonance is shown to be of the order of 5 to 10% in the current drive scenarios for the planned ITER experiment. If the single pass absorption in the centre can be made sufficiently high, the conversion at the Alfven resonance becomes negligible

Dual-drive Mach-Zehnder modulator-based reconfigurable and transparent spectral conversion for dense wavelength division multiplexing transmissions

NASA Astrophysics Data System (ADS)

Mao, Mingzhi; Qian, Chen; Cao, Bingyao; Zhang, Qianwu; Song, Yingxiong; Wang, Min

2017-09-01

A digital signal process enabled dual-drive Mach-Zehnder modulator (DD-MZM)-based spectral converter is proposed and extensively investigated to realize dynamically reconfigurable and high transparent spectral conversion. As another important innovation point of the paper, to optimize the converter performance, the optimum operation conditions of the proposed converter are deduced, statistically simulated, and experimentally verified. The optimum conditions supported-converter performances are verified by detail numerical simulations and experiments in intensity-modulation and direct-detection-based network in terms of frequency detuning range-dependent conversion efficiency, strict operation transparency for user signal characteristics, impact of parasitic components on the conversion performance, as well as the converted component waveform are almost nondistortion. It is also found that the converter has the high robustness to the input signal power, optical signal-to-noise ratio variations, extinction ratio, and driving signal frequency.

Clogging and transport of driven particles in asymmetric funnel arrays

NASA Astrophysics Data System (ADS)

Reichhardt, C. J. O.; Reichhardt, C.

2018-06-01

We numerically examine the flow and clogging of particles driven through asymmetric funnel arrays when the commensurability ratio of the number of particles per plaquette is varied. The particle–particle interactions are modeled with a soft repulsive potential that could represent vortex flow in type-II superconductors or driven charged colloids. The velocity-force curves for driving in the easy flow direction of the funnels exhibit a single depinning threshold; however, for driving in the hard flow direction, we find that there can be both negative mobility where the velocity decreases with increasing driving force as well as a reentrant pinning effect in which the particles flow at low drives but become pinned at intermediate drives. This reentrant pinning is associated with a transition from smooth 1D flow at low drives to a clogged state at higher drives that occurs when the particles cluster in a small number of plaquettes and block the flow. When the drive is further increased, particle rearrangements occur that cause the clog to break apart. We map out the regimes in which the pinned, flowing, and clogged states appear as a function of plaquette filling and drive. The clogged states remain robust at finite temperatures but develop intermittent bursts of flow in which a clog temporarily breaks apart but quickly reforms.

The risk of a safety-critical event associated with mobile device use in specific driving contexts.

PubMed

Fitch, Gregory M; Hanowski, Richard J; Guo, Feng

2015-01-01

We explored drivers' mobile device use and its associated risk of a safety-critical event (SCE) in specific driving contexts. Our premise was that the SCE risk associated with mobile device use increases when the driving task becomes demanding. Data from naturalistic driving studies involving commercial motor vehicle drivers and light vehicle drivers were partitioned into subsets representative of specific driving contexts. The subsets were generated using data set attributes that included level of service and relation to junction. These attributes were selected based on exogenous factors known to alter driving task demands. The subsets were analyzed using a case-cohort approach, which was selected to complement previous investigations of mobile device SCE risk using naturalistic driving data. Both commercial motor vehicle and light vehicle drivers varied as to how much they conversed on a mobile device but did not vary their engagement in visual-manual subtasks. Furthermore, commercial motor vehicle drivers conversed less frequently as the driving task demands increased, whereas light vehicle drivers did not. The risk of an SCE associated with mobile device use was dependent on the subtask performed and the driving context. Only visual-manual subtasks were associated with an increased SCE risk, whereas conversing was associated with a decreased risk in some driving contexts. Drivers' engagement in mobile device subtasks varies by driving context. The SCE risk associated with mobile device use is dependent on the types of subtasks performed and the driving context. The findings of this exploratory study can be applied to the design of driver-vehicle interfaces that mitigate distraction by preventing visual-manual subtasks while driving.

Clogging and transport of driven particles in asymmetric funnel arrays

DOE PAGES

Olson Reichhardt, Cynthia J.; Reichhardt, Charles

2018-05-03

In this paper, we numerically examine the flow and clogging of particles driven through asymmetric funnel arrays when the commensurability ratio of the number of particles per plaquette is varied. The particle-particle interactions are modeled with a soft repulsive potential that could represent vortex flow in type-II superconductors or driven charged colloids. The velocity-force curves for driving in the easy flow direction of the funnels exhibit a single depinning threshold; however, for driving in the hard flow direction, we find that there can be both negative mobility where the velocity decreases with increasing driving force as well as a reentrantmore » pinning effect in which the particles flow at low drives but become pinned at intermediate drives. This reentrant pinning is associated with a transition from smooth one-dimensional flow at low drives to a clogged state at higher drives that occurs when the particles cluster in a small number of plaquettes and block the flow. When the drive is further increased, particle rearrangements occur that cause the clog to break apart. We map out the regimes in which the pinned, flowing, and clogged states appear as a function of plaquette filling and drive. Finally, the clogged states remain robust at finite temperatures but develop intermittent bursts of flow in which a clog temporarily breaks apart but quickly reforms.« less

Clogging and transport of driven particles in asymmetric funnel arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olson Reichhardt, Cynthia J.; Reichhardt, Charles

In this paper, we numerically examine the flow and clogging of particles driven through asymmetric funnel arrays when the commensurability ratio of the number of particles per plaquette is varied. The particle-particle interactions are modeled with a soft repulsive potential that could represent vortex flow in type-II superconductors or driven charged colloids. The velocity-force curves for driving in the easy flow direction of the funnels exhibit a single depinning threshold; however, for driving in the hard flow direction, we find that there can be both negative mobility where the velocity decreases with increasing driving force as well as a reentrantmore » pinning effect in which the particles flow at low drives but become pinned at intermediate drives. This reentrant pinning is associated with a transition from smooth one-dimensional flow at low drives to a clogged state at higher drives that occurs when the particles cluster in a small number of plaquettes and block the flow. When the drive is further increased, particle rearrangements occur that cause the clog to break apart. We map out the regimes in which the pinned, flowing, and clogged states appear as a function of plaquette filling and drive. Finally, the clogged states remain robust at finite temperatures but develop intermittent bursts of flow in which a clog temporarily breaks apart but quickly reforms.« less

Twenty Years of Research on the Alcator C-Mod Tokamak

NASA Astrophysics Data System (ADS)

Greenwald, Martin

2013-10-01

Alcator C-Mod is a compact, high-field tokamak, whose unique design and operating parameters have produced a wealth of new and important results since its start in 1993, contributing data that extended tests of critical physical models into new parameter ranges and into new regimes. Using only RF for heating and current drive with innovative launching structures, C-Mod operates routinely at very high power densities. Research highlights include direct experimental observation of ICRF mode-conversion, ICRF flow drive, demonstration of Lower-Hybrid current drive at ITER-like densities and fields and, using a set of powerful new diagnostics, extensive validation of advanced RF codes. C-Mod spearheaded the development of the vertical-target divertor and has always operated with high-Z metal plasma facing components--an approach adopted for ITER. C-Mod has made ground-breaking discoveries in divertor physics and plasma-material interactions at reactor-like power and particle fluxes and elucidated the critical role of cross-field transport in divertor operation, edge flows and the tokamak density limit. C-Mod developed the I-mode and EDA H-mode regimes which have high performance without large ELMs and with pedestal transport self-regulated by short-wavelength electromagnetic waves. C-Mod has carried out pioneering studies of intrinsic rotation and found that self-generated flow shear can be strong enough to significantly modify transport. C-Mod made the first quantitative link between pedestal temperature and H-mode performance, showing that the observed self-similar temperature profiles were consistent with critical-gradient-length theories and followed up with quantitative tests of nonlinear gyrokinetic models. Disruption studies on C-Mod provided the first observation of non-axisymmetric halo currents and non-axisymmetric radiation in mitigated disruptions. Work supported by U.S. DoE

The relationship between cell phone use and management of driver fatigue: It's complicated.

PubMed

Saxby, Dyani Juanita; Matthews, Gerald; Neubauer, Catherine

2017-06-01

Voice communication may enhance performance during monotonous, potentially fatiguing driving conditions (Atchley & Chan, 2011); however, it is unclear whether safety benefits of conversation are outweighed by costs. The present study tested whether personalized conversations intended to simulate hands-free cell phone conversation may counter objective and subjective fatigue effects elicited by vehicle automation. A passive fatigue state (Desmond & Hancock, 2001), characterized by disengagement from the task, was induced using full vehicle automation prior to drivers resuming full control over the driving simulator. A conversation was initiated shortly after reversion to manual control. During the conversation an emergency event occurred. The fatigue manipulation produced greater task disengagement and slower response to the emergency event, relative to a control condition. Conversation did not mitigate passive fatigue effects; rather, it added worry about matters unrelated to the driving task. Conversation moderately improved vehicle control, as measured by SDLP, but it failed to counter fatigue-induced slowing of braking in response to an emergency event. Finally, conversation appeared to have a hidden danger in that it reduced drivers' insights into performance impairments when in a state of passive fatigue. Automation induced passive fatigue, indicated by loss of task engagement; yet, simulated cell phone conversation did not counter the subjective automation-induced fatigue. Conversation also failed to counter objective loss of performance (slower braking speed) resulting from automation. Cell phone conversation in passive fatigue states may impair drivers' awareness of their performance deficits. Practical applications: Results suggest that conversation, even using a hands-free device, may not be a safe way to reduce fatigue and increase alertness during transitions from automated to manual vehicle control. Copyright © 2017 Elsevier Ltd and National Safety Council. All rights reserved.

Examination of drivers' cell phone use behavior at intersections by using naturalistic driving data.

PubMed

Xiong, Huimin; Bao, Shan; Sayer, James; Kato, Kazuma

2015-09-01

Many driving simulator studies have shown that cell phone use while driving greatly degraded driving performance. In terms of safety analysis, many factors including drivers, vehicles, and driving situations need to be considered. Controlled or simulated studies cannot always account for the full effects of these factors, especially situational factors such as road condition, traffic density, and weather and lighting conditions. Naturalistic driving by its nature provides a natural and realistic way to examine drivers' behaviors and associated factors for cell phone use while driving. In this study, driving speed while using a cell phone (conversation or visual/manual tasks) was compared to two baselines (baseline 1: normal driving condition, which only excludes driving while using a cell phone, baseline 2: driving-only condition, which excludes all types of secondary tasks) when traversing an intersection. The outcomes showed that drivers drove slower when using a cell for both conversation and visual/manual (VM) tasks compared to baseline conditions. With regard to cell phone conversations, drivers were more likely to drive faster during the day time compared to night time driving and drive slower under moderate traffic compared to under sparse traffic situations. With regard to VM tasks, there was a significant interaction between traffic and cell phone use conditions. The maximum speed with VM tasks was significantly lower than that with baseline conditions under sparse traffic conditions. In contrast, the maximum speed with VM tasks was slightly higher than that with baseline driving under dense traffic situations. This suggests that drivers might self-regulate their behavior based on the driving situations and demand for secondary tasks, which could provide insights on driver distraction guidelines. With the rapid development of in-vehicle technology, the findings in this research could lead the improvement of human-machine interface (HMI) design as well. Copyright © 2015 Elsevier Ltd and National Safety Council. All rights reserved.

"The Power of the Oral Tradition: Giving Life to Words:" Conversations with Virginia Driving Hawk Sneve

ERIC Educational Resources Information Center

Young, Teresa; Henderson, Darwin L.

2013-01-01

Virginia Driving Hawk Sneve, a former English teacher and school counselor, is an award-winning author, best known for her children's books about the Rosebud Sioux life and culture, which combines history and legend to create culturally rich and authentic Native American stories. In this article, the authors share their conversations with Virginia…

Post and during event effect of cell phone talking and texting on driving performance--a driving simulator study.

PubMed

Thapa, Raju; Codjoe, Julius; Ishak, Sherif; McCarter, Kevin S

2015-01-01

A number of studies have been done in the field of driver distraction, specifically on the use of cell phone for either conversation or texting while driving. Researchers have focused on the driving performance of drivers when they were actually engaged in the task; that is, during the texting or phone conversation event. However, it is still unknown whether the impact of cell phone usages ceases immediately after the end of task. The primary objective of this article is to analyze the post-event effect of cell phone usage (texting and conversation) in order to verify whether the distracting effect lingers after the actual event has ceased. This study utilizes a driving simulator study of 36 participants to test whether a significant decrease in driver performance occurs during cell phone usage and after usage. Surrogate measures used to represent lateral and longitudinal control of the vehicle were standard deviation (SD) of lane position and mean velocity, respectively. RESULTS suggest that there was no significant decrease in driver performance (both lateral and longitudinal control) during and after the cell phone conversation. For the texting event, there were significant decreases in driver performance in both the longitudinal and lateral control of the vehicle during the actual texting task. The diminished longitudinal control ceased immediately after the texting event but the diminished lateral control lingered for an average of 3.38 s. The number of text messages exchanged did not affect the magnitude or duration of the diminished lateral control. The result indicates that the distraction and subsequent elevated crash risk of texting while driving linger even after the texting event has ceased. This finding has safety and policy implications in reducing distracted driving.

Power conversion process in magnetoelectric gyrators

NASA Astrophysics Data System (ADS)

Zhuang, X.; Leung, C. M.; Li, J.; Viehland, D.

2017-09-01

We have investigated the power conversion and loss processes in magnetoelectric gyrators. Two types of loss mechanisms were identified by using a transformer-gyrator structure, which transfers power between magnetic and magnetomechanical forms. A missing portion of the power in a gyrator was then identified to be a returned power from the load resistor under low drive conditions. Under high drive conditions, decreases in both the magnetostriction and mechanical quality factor resulted in additional inefficiencies. Power transfer efficiencies of greater than 70% and 50% were achieved for magnetoelectric (ME) gyrators based on Metglas/Pb(Zr,Ti)O3 laminated composites under low power drive and high power density drive (60 W/in.3) conditions, respectively.

Shifting attention across near and far spaces: implications for the use of hands-free cell phones while driving.

PubMed

Ferlazzo, Fabio; Fagioli, Sabrina; Di Nocera, Francesco; Sdoia, Stefano

2008-11-01

In three experiments, participants performed two tasks concurrently during driving. In the peripheral detection task, they responded manually to visual stimuli delivered through a LED placed on the internal rear mirror; in the conversation task, they were engaged in a conversation with a passenger, or through earphone-operated, loudspeaker-operated, or hand-held cell phones. Results showed that drivers were slower at responding to the visual stimuli when conversing through a hand-held cell phone or an earphone-operated cell phone than when conversing through a loudspeaker-operated cell phone or with a passenger. These results suggest that due to the brain coding the space into multiple representations, devices that make phone conversations taking place in the near, personal space make drivers slower at responding to visual stimuli, compared to devices that make the conversation occurring in a far space.

Rural migration: The driving force behind tropical deforestation on the settlement frontier

PubMed Central

Carr, David

2009-01-01

This paper reviews the state of knowledge and develops a conceptual model for researching frontier migration in the developing world with a focus on Latin America. Since only a small fraction of migrants move to forest frontiers, identifying people and place characteristics associated with this phenomenon could usefully inform policies aimed at forest conservation and rural development. Yet population scholars train their efforts on urban and international migration while land use/cover change researchers pay scant attention to these migration flows which directly antecede the most salient footprint of human occupation on the earth's surface: the conversion of forest to agricultural land. PMID:20485541

Mild Cognitive Impairment and driving: Does in-vehicle distraction affect driving performance?

PubMed

Beratis, Ion N; Pavlou, Dimosthenis; Papadimitriou, Eleonora; Andronas, Nikolaos; Kontaxopoulou, Dionysia; Fragkiadaki, Stella; Yannis, George; Papageorgiou, Sokratis G

2017-06-01

In-vehicle distraction is considered to be an important cause of road accidents. Drivers with Mild Cognitive Impairment (MCI), because of their attenuated cognitive resources, may be vulnerable to the effects of distraction; however, previous relevant research is lacking. The main objective of the current study was to explore the effect of in-vehicle distraction on the driving performance of MCI patients, by assessing their reaction time at unexpected incidents and accident probability. Thirteen patients with MCI (age: 64.5±7.2) and 12 cognitively intact individuals (age: 60.0±7.7), all active drivers were introduced in the study. The driving simulator experiment included three distraction conditions: (a) undistracted driving, (b) conversing with passenger and (c) conversing through a hand-held mobile phone. The mixed ANOVA models revealed a greater effect of distraction on MCI patients. Specifically, the use of mobile phone induced a more pronounced impact on reaction time and accident probability in the group of patients, as compared to healthy controls. On the other hand, in the driving condition "conversing with passenger" the interaction effects regarding reaction time and accident probability were not significant. Notably, the aforementioned findings concerning the MCI patients in the case of the mobile phone were observed despite the effort of the drivers to apply a compensatory strategy by reducing significantly their speed in this driving condition. Overall, the current findings indicate, for the first time, that a common driving practice, such as the use of mobile phone, may have a detrimental impact on the driving performance of individuals with MCI. Copyright © 2017. Published by Elsevier Ltd.

Electrokinetic energy conversion efficiency of viscoelastic fluids in a polyelectrolyte-grafted nanochannel.

PubMed

Jian, Yongjun; Li, Fengqin; Liu, Yongbo; Chang, Long; Liu, Quansheng; Yang, Liangui

2017-08-01

In order to conduct extensive investigation of energy harvesting capabilities of nanofluidic devices, we provide analytical solutions for streaming potential and electrokinetic energy conversion (EKEC) efficiency through taking the combined consequences of soft nanochannel, a rigid nanochannel whose surface is covered by charged polyelectrolyte layer, and viscoelastic rheology into account. The viscoelasticity of the fluid is considered by employing the Maxwell constitutive model when the forcing frequency of an oscillatory driving pressure flow matches with the inverse of the relaxation time scale of a typical viscoelastic fluid. We compare the streaming potential and EKEC efficiency with those of a rigid nanochannel, having zeta potential equal to the electrostatic potential at the solid-polyelectrolyte interface of the soft nanochannels. Within the present selected parameter ranges, it is shown that the different peaks of maximal streaming potential and EKEC efficiency for the rigid nanochannel are larger than those for the soft nanochannel when forcing frequencies of the driving pressure gradient are close to resonating frequencies. However, more enhanced streaming potential and EKEC efficiency for a soft nanochannel can be found in most of the regions away from these resonant frequencies. Moreover, the influence of several dimensionless parameters on EKEC efficiency is discussed in detail. Finally, within the given parametric regions, the maximum efficiency at some resonant frequency obtained in present analysis is about 25%. Copyright © 2017 Elsevier B.V. All rights reserved.

Effects of practice on interference from an auditory task while driving : a simulation study

DOT National Transportation Integrated Search

2004-12-01

Experimental research on the effects of cellular phone conversations on driving indicates that the phone task interferes with many driving-related functions, especially with older drivers. Limitations of past research have been that (1) the dual task...

A study on the flow characteristics of a direct drive turbine for energy conversion generation by experiment and CFD

NASA Astrophysics Data System (ADS)

Cho, Y. J.; Zullah, M. A.; Faizal, M.; Choi, Y. D.; Lee, Y. H.

2012-11-01

A variety of technologies has been proposed to capture the energy from waves. Some of the more promising designs are undergoing demonstration testing at commercial scales. Due to the complexity of most offshore wave energy devices and their motion response in different sea states, physical tank tests are common practice for WEC design. Full scale tests are also necessary, but are expensive and only considered once the design has been optimized. Computational Fluid Dynamics (CFD) is now recognized as an important complement to traditional physical testing techniques in offshore engineering. Once properly calibrated and validated to the problem, CFD offers a high density of test data and results in a reasonable timescale to assist with design changes and improvements to the device. The purpose of this study is to investigate the performance of a newly developed direct drive hydro turbine (DDT), which will be built in a caisson for extraction of wave energy. Experiments and CFD analysis are conducted to clarify the turbine performance and internal flow characteristics. The results show that commercial CFD code can be applied successfully to the simulation of the wave motion in the water tank. The performance of the turbine for wave energy converter is studied continuously for a ongoing project.

Structural equation model analysis for the evaluation of overall driving performance: A driving simulator study focusing on driver distraction.

PubMed

Papantoniou, Panagiotis

2018-04-03

The present research relies on 2 main objectives. The first is to investigate whether latent model analysis through a structural equation model can be implemented on driving simulator data in order to define an unobserved driving performance variable. Subsequently, the second objective is to investigate and quantify the effect of several risk factors including distraction sources, driver characteristics, and road and traffic environment on the overall driving performance and not in independent driving performance measures. For the scope of the present research, 95 participants from all age groups were asked to drive under different types of distraction (conversation with passenger, cell phone use) in urban and rural road environments with low and high traffic volume in a driving simulator experiment. Then, in the framework of the statistical analysis, a correlation table is presented investigating any of a broad class of statistical relationships between driving simulator measures and a structural equation model is developed in which overall driving performance is estimated as a latent variable based on several individual driving simulator measures. Results confirm the suitability of the structural equation model and indicate that the selection of the specific performance measures that define overall performance should be guided by a rule of representativeness between the selected variables. Moreover, results indicate that conversation with the passenger was not found to have a statistically significant effect, indicating that drivers do not change their performance while conversing with a passenger compared to undistracted driving. On the other hand, results support the hypothesis that cell phone use has a negative effect on driving performance. Furthermore, regarding driver characteristics, age, gender, and experience all have a significant effect on driving performance, indicating that driver-related characteristics play the most crucial role in overall driving performance. The findings of this study allow a new approach to the investigation of driving behavior in driving simulator experiments and in general. By the successful implementation of the structural equation model, driving behavior can be assessed in terms of overall performance and not through individual performance measures, which allows an important scientific step forward from piecemeal analyses to a sound combined analysis of the interrelationship between several risk factors and overall driving performance.

Electroviscous effect and electrokinetic energy conversion in time periodic pressure-driven flow through a parallel-plate nanochannel with surface charge-dependent slip

NASA Astrophysics Data System (ADS)

Buren, Mandula; Jian, Yongjun; Zhao, Yingchun; Chang, Long

2018-05-01

In this paper we analytically investigate the electroviscous effect and electrokinetic energy conversion in the time periodic pressure-driven flow of an incompressible viscous Newtonian liquid through a parallel-plate nanochannel with surface charge-dependent slip. Analytical and semi-analytical solutions for electric potential, velocity and streaming electric field are obtained and are utilized to compute electrokinetic energy conversion efficiency. The results show that velocity amplitude and energy conversion efficiency are reduced when the effect of surface charge on slip length is considered. The surface charge effect increases with zeta potential and ionic concentration. In addition, the energy conversion efficiency is large when the ratio of channel half-height to the electric double layer thickness is small. The boundary slip results in a large increase in energy conversion. Higher values of the frequency of pressure pulsation lead to higher values of the energy conversion efficiency. We also obtain the energy conversion efficiency in constant pressure-driven flow and find that the energy conversion efficiency in periodical pressure-driven flow becomes larger than that in constant pressure-driven flow when the frequency is large enough.

A parametric duration model of the reaction times of drivers distracted by mobile phone conversations.

PubMed

Haque, Md Mazharul; Washington, Simon

2014-01-01

The use of mobile phones while driving is more prevalent among young drivers-a less experienced cohort with elevated crash risk. The objective of this study was to examine and better understand the reaction times of young drivers to a traffic event originating in their peripheral vision whilst engaged in a mobile phone conversation. The CARRS-Q advanced driving simulator was used to test a sample of young drivers on various simulated driving tasks, including an event that originated within the driver's peripheral vision, whereby a pedestrian enters a zebra crossing from a sidewalk. Thirty-two licensed drivers drove the simulator in three phone conditions: baseline (no phone conversation), hands-free and handheld. In addition to driving the simulator each participant completed questionnaires related to driver demographics, driving history, usage of mobile phones while driving, and general mobile phone usage history. The participants were 21-26 years old and split evenly by gender. Drivers' reaction times to a pedestrian in the zebra crossing were modelled using a parametric accelerated failure time (AFT) duration model with a Weibull distribution. Also tested where two different model specifications to account for the structured heterogeneity arising from the repeated measures experimental design. The Weibull AFT model with gamma heterogeneity was found to be the best fitting model and identified four significant variables influencing the reaction times, including phone condition, driver's age, license type (provisional license holder or not), and self-reported frequency of usage of handheld phones while driving. The reaction times of drivers were more than 40% longer in the distracted condition compared to baseline (not distracted). Moreover, the impairment of reaction times due to mobile phone conversations was almost double for provisional compared to open license holders. A reduction in the ability to detect traffic events in the periphery whilst distracted presents a significant and measurable safety concern that will undoubtedly persist unless mitigated. Copyright © 2013 Elsevier Ltd. All rights reserved.

Integrated optical modulator for signal up-conversion over radio-on-fiber link.

PubMed

Kim, Woo-Kyung; Kwon, Soon-Woo; Jeong, Woo-Jin; Son, Geun-Sik; Lee, Kwang-Hyun; Choi, Woo-Young; Yang, Woo-Seok; Lee, Hyung-Man; Lee, Han-Young

2009-02-16

An integrated optical modulator, which consists of a dual-sideband suppressed carrier (DSB-SC) modulator cascaded with a single-sideband (SSB) modulator, is proposed for signal up-conversion over Radio-on-Fiber. Utilizing a single-drive domain inverted structure in both modulators, balanced modulations were obtained without complicated radio frequency (RF) driving circuits and delicate RF phase adjustments. Intermediate frequency (IF) band signal was up-conversed to 60GHz band by using the fabricated device and was transmitted over optical fiber. Experiment results show that the proposed device enables millimeter wave generation and signal transmission without any power penalty caused by chromatic dispersion.

Control of Advanced Reactor-Coupled Heat Exchanger System: Incorporation of Reactor Dynamics in System Response to Load Disturbances

DOE PAGES

Skavdahl, Isaac; Utgikar, Vivek; Christensen, Richard; ...

2016-05-24

We present an alternative control schemes for an Advanced High Temperature Reactor system consisting of a reactor, an intermediate heat exchanger, and a secondary heat exchanger (SHX) in this paper. One scheme is designed to control the cold outlet temperature of the SHX (T co) and the hot outlet temperature of the intermediate heat exchanger (T ho2) by manipulating the hot-side flow rates of the heat exchangers (F h/F h2) responding to the flow rate and temperature disturbances. The flow rate disturbances typically require a larger manipulation of the flow rates than temperature disturbances. An alternate strategy examines the controlmore » of the cold outlet temperature of the SHX (T co) only, since this temperature provides the driving force for energy production in the power conversion unit or the process application. The control can be achieved by three options: (1) flow rate manipulation; (2) reactor power manipulation; or (3) a combination of the two. The first option has a quicker response but requires a large flow rate change. The second option is the slowest but does not involve any change in the flow rates of streams. The final option appears preferable as it has an intermediate response time and requires only a minimal flow rate change.« less

Examining the impact of cell phone conversations on driving using meta-analytic techniques.

PubMed

Horrey, William J; Wickens, Christopher D

2006-01-01

The performance costs associated with cell phone use while driving were assessed meta-analytically using standardized measures of effect size along five dimensions. There have been many studies on the impact of cell phone use on driving, showing some mixed findings. Twenty-three studies (contributing 47 analysis entries) met the appropriate conditions for the meta-analysis. The statistical results from each of these studies were converted into effect sizes and combined in the meta-analysis. Overall, there were clear costs to driving performance when drivers were engaged in cell phone conversations. However, subsequent analyses indicated that these costs were borne primarily by reaction time tasks, with far smaller costs associated with tracking (lane-keeping) performance. Hands-free and handheld phones revealed similar patterns of results for both measures of performance. Conversation tasks tended to show greater costs than did information-processing tasks (e.g., word games). There was a similar pattern of results for passenger and remote (cell phone) conversations. Finally, there were some small differences between simulator and field studies, though both exhibited costs in performance for cell phone use. We suggest that (a) there are significant costs to driver reactions to external hazards or events associated with cell phone use, (b) hands-free cell phones do not eliminate or substantially reduce these costs, and (c) different research methodologies or performance measures may underestimate these costs. Potential applications of this research include the assessment of performance costs attributable to different types of cell phones, cell phone conversations, experimental measures, or methodologies.

Thin-thick quadrature frequency conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eimerl, D.

1985-02-07

The quadrature conversion scheme is a method of generating the second harmonic. The scheme, which uses two crystals in series, has several advantages over single-crystal or other two crystal schemes. The most important is that it is capable of high conversion efficiency over a large dynamic range of drive intensity and detuning angle.

Maximum efficiency of state-space models of nanoscale energy conversion devices

NASA Astrophysics Data System (ADS)

Einax, Mario; Nitzan, Abraham

2016-07-01

The performance of nano-scale energy conversion devices is studied in the framework of state-space models where a device is described by a graph comprising states and transitions between them represented by nodes and links, respectively. Particular segments of this network represent input (driving) and output processes whose properly chosen flux ratio provides the energy conversion efficiency. Simple cyclical graphs yield Carnot efficiency for the maximum conversion yield. We give general proof that opening a link that separate between the two driving segments always leads to reduced efficiency. We illustrate these general result with simple models of a thermoelectric nanodevice and an organic photovoltaic cell. In the latter an intersecting link of the above type corresponds to non-radiative carriers recombination and the reduced maximum efficiency is manifested as a smaller open-circuit voltage.

Maximum efficiency of state-space models of nanoscale energy conversion devices.

PubMed

Einax, Mario; Nitzan, Abraham

2016-07-07

The performance of nano-scale energy conversion devices is studied in the framework of state-space models where a device is described by a graph comprising states and transitions between them represented by nodes and links, respectively. Particular segments of this network represent input (driving) and output processes whose properly chosen flux ratio provides the energy conversion efficiency. Simple cyclical graphs yield Carnot efficiency for the maximum conversion yield. We give general proof that opening a link that separate between the two driving segments always leads to reduced efficiency. We illustrate these general result with simple models of a thermoelectric nanodevice and an organic photovoltaic cell. In the latter an intersecting link of the above type corresponds to non-radiative carriers recombination and the reduced maximum efficiency is manifested as a smaller open-circuit voltage.

Velocity-dependent emission factors of benzene, toluene and C 2-benzenes of a passenger car equipped with and without a regulated 3-way catalyst

NASA Astrophysics Data System (ADS)

Heeb, Norbert V.; Forss, Anna-Maria; Bach, Christian; Mattrel, Peter

Time-resolved chemical ionization mass spectrometry (CI-MS) has been used to investigate the velocity-dependent emission factors for benzene, toluene, the C 2-benzenes (xylenes and ethyl benzene) and nitrogen monoxide of a gasoline-driven passenger car (1.4 l, model year 1995) driven with or without catalytic exhaust gas treatment. A set of seven different driving cycles - including the European Driving Cycle (EDC), the US Urban (FTP 75) and the Highway driving cycles - with a total driving time of 12,000 s have been studied. From the obtained emission data, two sets of 15,300 and 17,200 data points which represent transient driving in the velocity range of 0-150 km h -1 and in an acceleration window of -2-3 m s -2 were explored to gain velocity-dependent emission factors. The passenger car, equipped with a regulated rhodium-platinum based three-way catalyst, showed optimal conversion efficiency (>95%) for benzene in the velocity range of 60-120 km h -1. The conversion of benzene was reduced (<80%) when driving below 50 km h -1 and the BTXE emissions significantly increased when driven at higher speed and engine load (>130 km h -1). Whereas the conversion efficiency for the class of C 2-benzenes was reduced to 10%, no net conversion could be found for toluene and benzene when driven above 130 km h -1. In contrast, the benzene and toluene emissions exceeded those of the untreated exhaust gas in the velocity range of 130-150 km h -1 by 50-92% and by 10-34%, respectively. Thus, benzene and toluene were formed across the examined three-way catalyst if the engine is operated for an extended time in a fuel-rich mode (lambda<1).

Hand-held cell phone use while driving legislation and observed driver behavior among population sub-groups in the United States.

PubMed

Rudisill, Toni M; Zhu, Motao

2017-05-12

Cell phone use behaviors are known to vary across demographic sub-groups and geographic locations. This study examined whether universal hand-held calling while driving bans were associated with lower road-side observed hand-held cell phone conversations across drivers of different ages (16-24, 25-59, ≥60 years), sexes, races (White, African American, or other), ruralities (suburban, rural, or urban), and regions (Northeast, Midwest, South, and West). Data from the 2008-2013 National Occupant Protection Use Survey were merged with states' cell phone use while driving legislation. The exposure was presence of a universal hand-held cell phone ban at time of observation. Logistic regression was used to assess the odds of drivers having a hand-held cell phone conversation. Sub-groups differences were assessed using models with interaction terms. When universal hand-held cell phone bans were effective, hand-held cell phone conversations were lower across all driver demographic sub-groups and regions. Sub-group differences existed among the sexes (p-value, <0.0001) and regions (p-value, 0.0003). Compared to states without universal hand-held cell phone bans, the adjusted odds ratio (aOR) of a driver hand-held phone conversation was 0.34 [95% confidence interval (CI): 0.28, 0.41] for females versus 0.47 (CI 0.40, 0.55) for males and 0.31 (CI 0.25, 0.38) for drivers in Western states compared to 0.47 (CI 0.30, 0.72) in the Northeast and 0.50 (CI 0.38, 0.66) in the South. The presence of universal hand-held cell phone bans were associated lower hand-held cell phone conversations across all driver sub-groups and regions. Hand-held phone conversations were particularly lower among female drivers and those from Western states when these bans were in effect. Public health interventions concerning hand-held cell phone use while driving could reasonably target all drivers.

Impact of Distracted Driving on Safety and Traffic Flow

PubMed Central

Stavrinos, Despina; Jones, Jennifer L.; Garner, Annie A.; Griffin, Russell; Franklin, Crystal A.; Ball, David; Welburn, Sharon C.; Ball, Karlene K.; Sisiopiku, Virginia P.; Fine, Philip R.

2015-01-01

Studies have documented a link between distracted driving and diminished safety; however, an association between distracted driving and traffic congestion has not been investigated in depth. The present study examined the behavior of teens and young adults operating a driving simulator while engaged in various distractions (i.e., cell phone, texting, and undistracted) and driving conditions (i.e., free flow, stable flow, and oversaturation). Seventy five participants 16 to 25 years of age (split into 2 groups: novice drivers and young adults) drove a STISIM simulator three times, each time with one of three randomly presented distractions. Each drive was designed to represent daytime scenery on a 4 lane divided roadway and included three equal roadway portions representing Levels of Service (LOS) A, C, and E as defined in the 2000 Highway Capacity Manual. Participants also completed questionnaires documenting demographics and driving history. Both safety and traffic flow related driving outcomes were considered. A Repeated Measures Multivariate Analysis of Variance was employed to analyze continuous outcome variables and a Generalized Estimate Equation (GEE) poisson model was used to analyze count variables. Results revealed that, in general more lane deviations and crashes occurred during texting. Distraction (in most cases, text messaging) had a significantly negative impact on traffic flow, such that participants exhibited greater fluctuation in speed, changed lanes significantly fewer times, and took longer to complete the scenario. In turn, more simulated vehicles passed the participant drivers while they were texting or talking on a cell phone than while undistracted. The results indicate that distracted driving, particularly texting, may lead to reduced safety and traffic flow, thus having a negative impact on traffic operations. No significant differences were detected between age groups, suggesting that all drivers, regardless of age, may drive in a manner that impacts safety and traffic flow negatively when distracted. PMID:23465745

Impact of distracted driving on safety and traffic flow.

PubMed

Stavrinos, Despina; Jones, Jennifer L; Garner, Annie A; Griffin, Russell; Franklin, Crystal A; Ball, David; Welburn, Sharon C; Ball, Karlene K; Sisiopiku, Virginia P; Fine, Philip R

2013-12-01

Studies have documented a link between distracted driving and diminished safety; however, an association between distracted driving and traffic congestion has not been investigated in depth. The present study examined the behavior of teens and young adults operating a driving simulator while engaged in various distractions (i.e., cell phone, texting, and undistracted) and driving conditions (i.e., free flow, stable flow, and oversaturation). Seventy five participants 16-25 years of age (split into 2 groups: novice drivers and young adults) drove a STISIM simulator three times, each time with one of three randomly presented distractions. Each drive was designed to represent daytime scenery on a 4 lane divided roadway and included three equal roadway portions representing Levels of Service (LOS) A, C, and E as defined in the 2000 Highway Capacity Manual. Participants also completed questionnaires documenting demographics and driving history. Both safety and traffic flow related driving outcomes were considered. A Repeated Measures Multivariate Analysis of Variance was employed to analyze continuous outcome variables and a Generalized Estimate Equation (GEE) Poisson model was used to analyze count variables. Results revealed that, in general more lane deviations and crashes occurred during texting. Distraction (in most cases, text messaging) had a significantly negative impact on traffic flow, such that participants exhibited greater fluctuation in speed, changed lanes significantly fewer times, and took longer to complete the scenario. In turn, more simulated vehicles passed the participant drivers while they were texting or talking on a cell phone than while undistracted. The results indicate that distracted driving, particularly texting, may lead to reduced safety and traffic flow, thus having a negative impact on traffic operations. No significant differences were detected between age groups, suggesting that all drivers, regardless of age, may drive in a manner that impacts safety and traffic flow negatively when distracted. Copyright © 2013 Elsevier Ltd. All rights reserved.

Flow enhancement of deformable self-driven objects by countercurrent

NASA Astrophysics Data System (ADS)

Mashiko, Takashi; Fujiwara, Takashi

2016-10-01

We report numerical simulations of the mixed flows of two groups of deformable self-driven objects. The objects belonging to the group A (B) have drift coefficient D =DA (DB), where a positive (negative) value of D denotes the rightward (leftward) driving force. For co-current flows (DA ,DB > 0), the result is rather intuitive: the net flow of one group (QA) increases if the driving force of the other group is stronger than its own driving force (i.e., DB >DA), and decreases otherwise (DB

Distracted driving and associated crash risks.

DOT National Transportation Integrated Search

2014-10-01

Distracted driving is a dangerous epidemic that has resulted in deaths and injuries in crashes throughout the U.S. Research is : needed to understand whether common cognitive tasks such as texting, handheld cell phone conversation, and front-seat : p...

Investigation of the effect of Alfven resonance absorption on fast wave current drive in ITER

NASA Astrophysics Data System (ADS)

Alava, M. J.; Heikkinen, J. A.; Hellsten, T.

The use of frequencies below the ion cyclotron frequency of minority ion species or second harmonic of majority species has been proposed for fast wave current drive in order to reduce or to avoid ion cyclotron damping. For these scenarios, the Alfven resonance can appear on the high field side of a tokamak. The presence of this resonance causes parasitic absorption competing with the electron Landau damping and transit time magnetic pumping responsible for the fast wave current drive. In the present study, the mode conversion at the Alfven resonance is shown to be of the order of 5 to 10 percent in the current drive scenarios for the planned International Thermonuclear Experimental Reactor (ITER) experiment. However, if the single pass absorption in the center can be made sufficiently high, the conversion at the Alfven resonance becomes negligible.

Driver distraction : eye glance analysis and conversation workload : [research brief].

DOT National Transportation Integrated Search

2015-11-01

The objective of this project was to: : Assess the risk of performing a secondary task : while driving a commercial motor vehicle (CMV). : Better understand the relationship of conversation : workload and visual distraction during mobile : ph...

Pressure Loss Predictions of the Reactor Simulator Subsystem at NASA GRC

NASA Technical Reports Server (NTRS)

Reid, Terry V.

2015-01-01

Testing of the Fission Power System (FPS) Technology Demonstration Unit (TDU) is being conducted at NASA GRC. The TDU consists of three subsystems: the Reactor Simulator (RxSim), the Stirling Power Conversion Unit (PCU), and the Heat Exchanger Manifold (HXM). An Annular Linear Induction Pump (ALIP) is used to drive the working fluid. A preliminary version of the TDU system (which excludes the PCU for now), is referred to as the RxSim subsystem and was used to conduct flow tests in Vacuum Facility 6 (VF 6). In parallel, a computational model of the RxSim subsystem was created based on the CAD model and was used to predict loop pressure losses over a range of mass flows. This was done to assess the ability of the pump to meet the design intent mass flow demand. Measured data indicates that the pump can produce 2.333 kg/sec of flow, which is enough to supply the RxSim subsystem with a nominal flow of 1.75 kg/sec. Computational predictions indicated that the pump could provide 2.157 kg/sec (using the Spalart-Allmaras turbulence model), and 2.223 kg/sec (using the k-? turbulence model). The computational error of the predictions for the available mass flow is -0.176 kg/sec (with the S-A turbulence model) and -0.110 kg/sec (with the k-epsilon turbulence model) when compared to measured data.

Multi-megawatt power system trade study

NASA Astrophysics Data System (ADS)

Longhurst, Glen R.; Schnitzler, Bruce G.; Parks, Benjamin T.

2002-01-01

A concept study was undertaken to evaluate potential multi-megawatt power sources for nuclear electric propulsion. The nominal electric power requirement was set at 15 MWe with an assumed mission profile of 120 days at full power, 60 days in hot standby, and another 120 days of full power, repeated several times for 7 years of service. Two configurations examined were (1) a gas-cooled reactor based on the NERVA Derivative design, operating a closed cycle Brayton power conversion system; and (2) a molten metal-cooled reactor based on SP-100 technology, driving a boiling potassium Rankine power conversion system. This study considered the relative merits of these two systems, seeking to optimize the specific mass. Conclusions were that either concept appeared capable of reaching the specific mass goal of 3-5 kg/kWe estimated to be needed for this class of mission, though neither could be realized without substantial development in reactor fuels technology, thermal radiator mass and volume efficiency, and power conversion and distribution electronics and systems capable of operating at high temperatures. The gas-Brayton system showed a specific mass advantage (3.17 vs 6.43 kg/kWe for the baseline cases) under the set of assumptions used and eliminated the need to deal with two-phase working fluid flows in the microgravity environment of space. .

Two-lane traffic-flow model with an exact steady-state solution.

PubMed

Kanai, Masahiro

2010-12-01

We propose a stochastic cellular-automaton model for two-lane traffic flow based on the misanthrope process in one dimension. The misanthrope process is a stochastic process allowing for an exact steady-state solution; hence, we have an exact flow-density diagram for two-lane traffic. In addition, we introduce two parameters that indicate, respectively, driver's driving-lane preference and passing-lane priority. Due to the additional parameters, the model shows a deviation of the density ratio for driving-lane use and a biased lane efficiency in flow. Then, a mean-field approach explicitly describes the asymmetric flow by the hop rates, the driving-lane preference, and the passing-lane priority. Meanwhile, the simulation results are in good agreement with an observational data, and we thus estimate these parameters. We conclude that the proposed model successfully produces two-lane traffic flow particularly with the driving-lane preference and the passing-lane priority.

Computational Fluid Dynamics (CFD) simulations of a Heisenberg Vortex Tube

NASA Astrophysics Data System (ADS)

Bunge, Carl; Sitaraman, Hariswaran; Leachman, Jake

2017-11-01

A 3D Computational Fluid Dynamics (CFD) simulation of a Heisenberg Vortex Tube (HVT) is performed to estimate cooling potential with cryogenic hydrogen. The main mechanism driving operation of the vortex tube is the use of fluid power for enthalpy streaming in a highly turbulent swirl in a dual-outlet tube. This enthalpy streaming creates a temperature separation between the outer and inner regions of the flow. Use of a catalyst on the peripheral wall of the centrifuge enables endothermic conversion of para-ortho hydrogen to aid primary cooling. A κ- ɛ turbulence model is used with a cryogenic, non-ideal equation of state, and para-orthohydrogen species evolution. The simulations are validated with experiments and strategies for parametric optimization of this device are presented.

Efficiency of energy conversion in model biological pumps. Optimization by linear nonequilibrium thermodynamic relations.

PubMed

Stucki, J W; Compiani, M; Caplan, S R

1983-09-01

Experimental investigations showed linear relations between flows and forces in some biological energy converters operating far from equilibrium. This observation cannot be understood on the basis of conventional nonequilibrium thermodynamics. Therefore, the efficiencies of a linear and a nonlinear mode of operation of an energy converter (a hypothetical redox-driven H+ pump) were compared. This comparison revealed that at physiological values of the forces and degrees of coupling (1) the force ratio permitting optimal efficiency was much higher in the linear than in the nonlinear mode and (2) the linear mode of operation was at least 10(6)-times more efficient that the nonlinear one. These observations suggest that the experimentally observed linear relations between flows and forces, particularly in the case of oxidative phosphorylation, may be due to a feedback regulation maintaining linear thermodynamic relations far from equilibrium. This regulation may have come about as the consequence of an evolutionary drive towards higher efficiency.

Age related changes in cognitive response style in the driving task.

DOT National Transportation Integrated Search

2009-11-16

The degree and manner in which cellular phone conversations and other cognitive distractions affect driving performance remains an area of great interest. It is well known that cellular phone usage adversely impacts safety (Redelmeier &Tibshirani, 19...

Conversational Flow Promotes Solidarity

PubMed Central

Koudenburg, Namkje; Postmes, Tom; Gordijn, Ernestine H.

2013-01-01

Social interaction is fundamental to the development of various aspects of “we-ness”. Previous research has focused on the role the content of interaction plays in establishing feelings of unity, belongingness and shared reality (a cluster of variables referred to as solidarity here). The present paper is less concerned with content, but focuses on the form of social interaction. We propose that the degree to which conversations flow smoothly or not is, of itself, a cue to solidarity. We test this hypothesis in samples of unacquainted and acquainted dyads who communicate via headsets. Conversational flow is disrupted by introducing a delay in the auditory feedback (vs. no delay). Results of three studies show that smoothly coordinated conversations (compared with disrupted conversations and a control condition) increase feelings of belonging and perceptions of group entitativity, independently of conversation content. These effects are driven by the subjective experience of conversational flow. Our data suggest that this process occurs largely beyond individuals' control. We conclude that the form of social interaction is a powerful cue for inferring group solidarity. Implications for the impact of modern communication technology on developing a shared social identity are discussed. PMID:24265683

Conversational flow promotes solidarity.

PubMed

Koudenburg, Namkje; Postmes, Tom; Gordijn, Ernestine H

2013-01-01

Social interaction is fundamental to the development of various aspects of "we-ness". Previous research has focused on the role the content of interaction plays in establishing feelings of unity, belongingness and shared reality (a cluster of variables referred to as solidarity here). The present paper is less concerned with content, but focuses on the form of social interaction. We propose that the degree to which conversations flow smoothly or not is, of itself, a cue to solidarity. We test this hypothesis in samples of unacquainted and acquainted dyads who communicate via headsets. Conversational flow is disrupted by introducing a delay in the auditory feedback (vs. no delay). Results of three studies show that smoothly coordinated conversations (compared with disrupted conversations and a control condition) increase feelings of belonging and perceptions of group entitativity, independently of conversation content. These effects are driven by the subjective experience of conversational flow. Our data suggest that this process occurs largely beyond individuals' control. We conclude that the form of social interaction is a powerful cue for inferring group solidarity. Implications for the impact of modern communication technology on developing a shared social identity are discussed.

Recent Advances in Photoelectrochemical Applications of Silicon Materials for Solar-to-Chemicals Conversion.

PubMed

Zhang, Doudou; Shi, Jingying; Zi, Wei; Wang, Pengpeng; Liu, Shengzhong Frank

2017-11-23

Photoelectrochemical (PEC) technology for the conversion of solar energy into chemicals requires cost-effective photoelectrodes to efficiently and stably drive anodic and/or cathodic half-reactions to complete the overall reactions for storing solar energy in chemical bonds. The shared properties among semiconducting photoelectrodes and photovoltaic (PV) materials are light absorption, charge separation, and charge transfer. Earth-abundant silicon materials have been widely applied in the PV industry, and have demonstrated their efficiency as alternative photoabsorbers for photoelectrodes. Many efforts have been made to fabricate silicon photoelectrodes with enhanced performance, and significant progress has been achieved in recent years. Herein, recent developments in crystalline and thin-film silicon-based photoelectrodes (including amorphous, microcrystalline, and nanocrystalline silicon) immersed in aqueous solution for PEC hydrogen production from water splitting are summarized, as well as applications in PEC CO 2 reduction and PEC regeneration of discharged species in redox flow batteries. Silicon is an ideal material for the cost-effective production of solar chemicals through PEC methods. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nature-driven photochemistry for catalytic solar hydrogen production: a Photosystem I-transition metal catalyst hybrid.

PubMed

Utschig, Lisa M; Silver, Sunshine C; Mulfort, Karen L; Tiede, David M

2011-10-19

Solar energy conversion of water into the environmentally clean fuel hydrogen offers one of the best long-term solutions for meeting future energy demands. Nature provides highly evolved, finely tuned molecular machinery for solar energy conversion that exquisitely manages photon capture and conversion processes to drive oxygenic water-splitting and carbon fixation. Herein, we use one of Nature's specialized energy-converters, the Photosystem I (PSI) protein, to drive hydrogen production from a synthetic molecular catalyst comprised of inexpensive, earth-abundant materials. PSI and a cobaloxime catalyst self-assemble, and the resultant complex rapidly produces hydrogen in aqueous solution upon exposure to visible light. This work establishes a strategy for enhancing photosynthetic efficiency for solar fuel production by augmenting natural photosynthetic systems with synthetically tunable abiotic catalysts.

Fuel pumping system and method

DOEpatents

Shafer, Scott F [Morton, IL; Wang, Lifeng ,

2006-12-19

A fuel pumping system that includes a pump drive is provided. A first pumping element is operatively connected to the pump drive and is operable to generate a first flow of pressurized fuel. A second pumping element is operatively connected to the pump drive and is operable to generate a second flow of pressurized fuel. A first solenoid is operatively connected to the first pumping element and is operable to vary at least one of a fuel pressure and a fuel flow rate of the first flow of pressurized fuel. A second solenoid is operatively connected to the second pumping element and is operable to vary at least one of a fuel pressure and a fuel flow rate of the second flow of pressurized fuel.

Fuel Pumping System And Method

DOEpatents

Shafer, Scott F.; Wang, Lifeng

2005-12-13

A fuel pumping system that includes a pump drive is provided. A first pumping element is operatively connected to the pump drive and is operable to generate a first flow of pressurized fuel. A second pumping element is operatively connected to the pump drive and is operable to generate a second flow of pressurized fuel. A first solenoid is operatively connected to the first pumping element and is operable to vary at least one of a fuel pressure and a fuel flow rate of the first flow of pressurized fuel. A second solenoid is operatively connected to the second pumping element and is operable to vary at least one of a fuel pressure and a fuel flow rate of the second flow of pressurized fuel.

Steering the conversation: A linguistic exploration of natural language interactions with a digital assistant during simulated driving.

PubMed

Large, David R; Clark, Leigh; Quandt, Annie; Burnett, Gary; Skrypchuk, Lee

2017-09-01

Given the proliferation of 'intelligent' and 'socially-aware' digital assistants embodying everyday mobile technology - and the undeniable logic that utilising voice-activated controls and interfaces in cars reduces the visual and manual distraction of interacting with in-vehicle devices - it appears inevitable that next generation vehicles will be embodied by digital assistants and utilise spoken language as a method of interaction. From a design perspective, defining the language and interaction style that a digital driving assistant should adopt is contingent on the role that they play within the social fabric and context in which they are situated. We therefore conducted a qualitative, Wizard-of-Oz study to explore how drivers might interact linguistically with a natural language digital driving assistant. Twenty-five participants drove for 10 min in a medium-fidelity driving simulator while interacting with a state-of-the-art, high-functioning, conversational digital driving assistant. All exchanges were transcribed and analysed using recognised linguistic techniques, such as discourse and conversation analysis, normally reserved for interpersonal investigation. Language usage patterns demonstrate that interactions with the digital assistant were fundamentally social in nature, with participants affording the assistant equal social status and high-level cognitive processing capability. For example, participants were polite, actively controlled turn-taking during the conversation, and used back-channelling, fillers and hesitation, as they might in human communication. Furthermore, participants expected the digital assistant to understand and process complex requests mitigated with hedging words and expressions, and peppered with vague language and deictic references requiring shared contextual information and mutual understanding. Findings are presented in six themes which emerged during the analysis - formulating responses; turn-taking; back-channelling, fillers and hesitation; vague language; mitigating requests and politeness and praise. The results can be used to inform the design of future in-vehicle natural language systems, in particular to help manage the tension between designing for an engaging dialogue (important for technology acceptance) and designing for an effective dialogue (important to minimise distraction in a driving context). Copyright © 2017 Elsevier Ltd. All rights reserved.

Analyses of conversion efficiency in high-speed clock recovery based on Mach-Zehnder modulator

NASA Astrophysics Data System (ADS)

Dong, H.; Sun, H.; Zhu, G.; Dutta, N. K.

2006-09-01

In this paper, detailed analyses of the conversion efficiency in high-speed clock recovery based on Mach-Zehnder (MZ) modulator has been carried out. The theoretical results show the conversion efficiency changes with RF driving power and the mixing order. For high order clock recovery, the cascaded MZ modulator provides higher conversion efficiency. A study of clock recovery at 160 Gb/s using the cascaded MZ modulator has been carried out. The experimental results agree with the results of the analysis.

IDS conversions to for-profit status: structuring the deal.

PubMed

Jaques, D A

1998-10-01

Not-for-profit integrated delivery systems (IDSs) may convert assets to for-profit status in a variety of ways, but typically choose from three basic conversion structures: sale of assets, joint ventures, and lease or management agreements. To select the optimal conversion structure, not-for-profit IDS executives should understand the forces driving their organization's desire or need to effect such a conversion and examine the legal, business, and political implications of each option in light of the organization's particular circumstances.

In vitro validation of a Pitot-based flow meter for the measurement of respiratory volume and flow in large animal anaesthesia.

PubMed

Moens, Yves P S; Gootjes, Peter; Ionita, Jean-Claude; Heinonen, Erkki; Schatzmann, Urs

2009-05-01

To remodel and validate commercially available monitors and their Pitot tube-based flow sensors for use in large animals, using in vitro techniques. Prospective, in vitro experiment. Both the original and the remodelled sensor were studied with a reference flow generator. Measurements were taken of the static flow-pressure relationship and linearity of the flow signal. Sensor airway resistance was calculated. Following recalibration of the host monitor, volumes ranging from 1 to 7 L were generated by a calibration syringe, and bias and precision of spirometric volume was determined. Where manual recalibration was not available, a conversion factor for volume measurement was determined. The influence of gas composition mixture and peak flow on the conversion factor was studied. Both the original and the remodelled sensor showed similar static flow-pressure relationships and linearity of the flow signal. Mean bias (%) of displayed values compared with the reference volume of 3, 5 and 7 L varied between -0.4% and +2.4%, and this was significantly smaller than that for 1 L (4.8% to +5.0%). Conversion factors for 3, 5 and 7 L were very similar (mean 6.00 +/- 0.2, range 5.91-6.06) and were not significantly influenced by the gas mixture used. Increasing peak flow caused a small decrease in the conversion factor. Volume measurement error and conversion factors for inspiration and expiration were close to identity. The combination of the host monitor with the remodelled flow sensor allowed accurate in vitro measurement of flows and volumes in a range expected during large animal anaesthesia. This combination has potential as a reliable spirometric monitor for use during large animal anaesthesia.

Pressure Loss Predictions of the Reactor Simulator Subsystem at NASA Glenn Research Center

NASA Technical Reports Server (NTRS)

Reid, Terry V.

2016-01-01

Testing of the Fission Power System (FPS) Technology Demonstration Unit (TDU) is being conducted at NASA Glenn Research Center. The TDU consists of three subsystems: the reactor simulator (RxSim), the Stirling Power Conversion Unit (PCU), and the heat exchanger manifold (HXM). An annular linear induction pump (ALIP) is used to drive the working fluid. A preliminary version of the TDU system (which excludes the PCU for now) is referred to as the "RxSim subsystem" and was used to conduct flow tests in Vacuum Facility 6 (VF 6). In parallel, a computational model of the RxSim subsystem was created based on the computer-aided-design (CAD) model and was used to predict loop pressure losses over a range of mass flows. This was done to assess the ability of the pump to meet the design intent mass flow demand. Measured data indicates that the pump can produce 2.333 kg/sec of flow, which is enough to supply the RxSim subsystem with a nominal flow of 1.75 kg/sec. Computational predictions indicated that the pump could provide 2.157 kg/sec (using the Spalart-Allmaras (S?A) turbulence model) and 2.223 kg/sec (using the k- turbulence model). The computational error of the predictions for the available mass flow is ?0.176 kg/sec (with the S-A turbulence model) and -0.110 kg/sec (with the k- turbulence model) when compared to measured data.

Proposed low-temperature solar engine

NASA Technical Reports Server (NTRS)

Peoples, J. A.; Kearns, G. B.

1976-01-01

Engine, proposed for conversion of Sun's heat to motion without need for heat pumps and associated equipment, uses expansion and contraction of aluminum rod to drive tow out-of-phase windlasses. Linear displacement of 0.076 cm in rod will exert sufficient force to drive pumps, generators, and compressors.

Examining the impact of cell phone conversations on driving using meta-analytic techniques

DOT National Transportation Integrated Search

2006-01-01

Synopsis Younger and older drivers conversing on a hands-free cell phone were found to have slower responses to random braking by the vehicle ahead. Cell phone use slowed the younger drivers responses to an extent that they were equivalent t...

Psychological predictors of college students' cell phone use while driving.

PubMed

Schlehofer, Michèle M; Thompson, Suzanne C; Ting, Sarah; Ostermann, Sharon; Nierman, Angela; Skenderian, Jessica

2010-07-01

Despite the known risk, many people talk on a phone while driving. This study explored psychological predictors of cell phone use while driving. College students (final N=69) completed a survey and predicted their driving performance both with and without a simultaneous phone conversation. Their actual performance on a driving simulator was then assessed. Cell phone use reduced performance on the simulation task. Further, perceiving oneself as good at compensating for driving distractions, overestimating one's performance on the driving simulator, and high illusory control predicted more frequent cell phone use while driving in everyday life. Finally, those who talked more frequently on a phone while driving had poorer real-world driving records. These findings suggest illusory control and positive illusions partly explain driver's decisions of whether to use cell phones while driving. Copyright 2010 Elsevier Ltd. All rights reserved.

Heat pipe cooled heat rejection subsystem modelling for nuclear electric propulsion

NASA Astrophysics Data System (ADS)

Moriarty, Michael P.

1993-11-01

NASA LeRC is currently developing a FORTRAN based computer model of a complete nuclear electric propulsion (NEP) vehicle that can be used for piloted and cargo missions to the Moon or Mars. Proposed designs feature either a Brayton or a K-Rankine power conversion cycle to drive a turbine coupled with rotary alternators. Both ion and magnetoplasmodynamic (MPD) thrusters will be considered in the model. In support of the NEP model, Rocketdyne is developing power conversion, heat rejection, and power management and distribution (PMAD) subroutines. The subroutines will be incorporated into the NEP vehicle model which will be written by NASA LeRC. The purpose is to document the heat pipe cooled heat rejection subsystem model and its supporting subroutines. The heat pipe cooled heat rejection subsystem model is designed to provide estimate of the mass and performance of the equipment used to reject heat from Brayton and Rankine cycle power conversion systems. The subroutine models the ductwork and heat pipe cooled manifold for a gas cooled Brayton; the heat sink heat exchanger, liquid loop piping, expansion compensator, pump and manifold for a liquid loop cooled Brayton; and a shear flow condenser for a K-Rankine system. In each case, the final heat rejection is made by way of a heat pipe radiator. The radiator is sized to reject the amount of heat necessary.

Heat pipe cooled heat rejection subsystem modelling for nuclear electric propulsion

NASA Technical Reports Server (NTRS)

Moriarty, Michael P.

1993-01-01

NASA LeRC is currently developing a FORTRAN based computer model of a complete nuclear electric propulsion (NEP) vehicle that can be used for piloted and cargo missions to the Moon or Mars. Proposed designs feature either a Brayton or a K-Rankine power conversion cycle to drive a turbine coupled with rotary alternators. Both ion and magnetoplasmodynamic (MPD) thrusters will be considered in the model. In support of the NEP model, Rocketdyne is developing power conversion, heat rejection, and power management and distribution (PMAD) subroutines. The subroutines will be incorporated into the NEP vehicle model which will be written by NASA LeRC. The purpose is to document the heat pipe cooled heat rejection subsystem model and its supporting subroutines. The heat pipe cooled heat rejection subsystem model is designed to provide estimate of the mass and performance of the equipment used to reject heat from Brayton and Rankine cycle power conversion systems. The subroutine models the ductwork and heat pipe cooled manifold for a gas cooled Brayton; the heat sink heat exchanger, liquid loop piping, expansion compensator, pump and manifold for a liquid loop cooled Brayton; and a shear flow condenser for a K-Rankine system. In each case, the final heat rejection is made by way of a heat pipe radiator. The radiator is sized to reject the amount of heat necessary.

A study of power generation from a low-cost hydrokinetic energy system

NASA Astrophysics Data System (ADS)

Davila Vilchis, Juana Mariel

The kinetic energy in river streams, tidal currents, or other artificial water channels has been used as a feasible source of renewable power through different conversion systems. Thus, hydrokinetic energy conversion systems are attracting worldwide interest as another form of distributed alternative energy. Because these systems are still in early stages of development, the basic approaches need significant research. The main challenges are not only to have efficient systems, but also to convert energy more economically so that the cost-benefit analysis drives the growth of this alternative energy form. One way to view this analysis is in terms of the energy conversion efficiency per unit cost. This study presents a detailed assessment of a prototype hydrokinetic energy system along with power output costs. This experimental study was performed using commercial low-cost blades of 20 in diameter inside a tank with water flow speed up to 1.3 m/s. The work was divided into two stages: (a) a fixed-pitch blade configuration, using a radial permanent magnet generator (PMG), and (b) the same hydrokinetic turbine, with a variable-pitch blade and an axial-flux PMG. The results indicate that even though the efficiency of a simple blade configuration is not high, the power coefficient is in the range of other, more complicated designs/prototypes. Additionally, the low manufacturing and operation costs of this system offer an option for low-cost distributed power applications.

Analysis of the effect of older drivers’ driving behaviors on traffic flow based on a modified CA model

NASA Astrophysics Data System (ADS)

Jian, Mei-Ying; Shi, Jing; Liu, Yang

2016-09-01

As the global population ages, there are more and more older drivers on the road. The decline in driving performance of older drivers may influence the properties of traffic flow and safety. The purpose of this paper is to investigate the effect of older drivers’ driving behaviors on traffic flow. A modified cellular automaton (CA) model which takes driving behaviors of older drivers into account is proposed. The simulation results indicate that older drivers’ driving behaviors induce a reduction in traffic flow especially when the density is higher than 15 vehicles per km per lane and an increase in Lane-changing frequency. The analysis of stability shows that a number of disturbances could frequently emerge, be propagated and eventually dissipate in this modified model. The results also reflect that with the increase of older drivers on the road, the probability of the occurrence of rear-end collisions increases greatly and obviously. Furthermore, the value of acceleration influences the traffic flow and safety significantly. These results provide the theoretical basis and reference for the traffic management departments to develop traffic management measure in the aging society.

Electrically driving large magnetic Reynolds number flows on the Madison plasma dynamo experiment

NASA Astrophysics Data System (ADS)

Weisberg, David; Wallace, John; Peterson, Ethan; Endrezzi, Douglass; Forest, Cary B.; Desangles, Victor

2015-11-01

Electrically-driven plasma flows, predicted to excite a large-scale dynamo instability, have been generated in the Madison plasma dynamo experiment (MPDX), at the Wisconsin Plasma Astrophysics Laboratory. Numerical simulations show that certain topologies of these simply-connected flows may be optimal for creating a plasma dynamo and predict critical thresholds as low as Rmcrit =μ0 σLV = 250 . MPDX plasmas are shown to exceed this critical Rm , generating large (L = 1 . 4 m), warm (Te > 10 eV), unmagnetized (MA > 1) plasmas where Rm < 600 . Plasma flow is driven using ten thermally emissive LaB6 cathodes which generate a J × B torque in Helium plasmas. Detailed Mach probe measurements of plasma velocity for two flow topologies will be presented: edge-localized drive using the multi-cusp boundary field, and volumetric drive using an axial Helmholtz field. Radial velocity profiles show that edge-driven flow is established via ion viscosity but is limited by a volumetric neutral drag force (χ ~ 1 / (ντin)), and measurements of velocity shear compare favorably to Braginskii transport theory. Volumetric flow drive is shown to produce stronger velocity shear, and is characterized by the radial potential gradient as determined by global charge balance.

TopoDrive and ParticleFlow--Two Computer Models for Simulation and Visualization of Ground-Water Flow and Transport of Fluid Particles in Two Dimensions

USGS Publications Warehouse

Hsieh, Paul A.

2001-01-01

This report serves as a user?s guide for two computer models: TopoDrive and ParticleFlow. These two-dimensional models are designed to simulate two ground-water processes: topography-driven flow and advective transport of fluid particles. To simulate topography-driven flow, the user may specify the shape of the water table, which bounds the top of the vertical flow section. To simulate transport of fluid particles, the model domain is a rectangle with overall flow from left to right. In both cases, the flow is under steady state, and the distribution of hydraulic conductivity may be specified by the user. The models compute hydraulic head, ground-water flow paths, and the movement of fluid particles. An interactive visual interface enables the user to easily and quickly explore model behavior, and thereby better understand ground-water flow processes. In this regard, TopoDrive and ParticleFlow are not intended to be comprehensive modeling tools, but are designed for modeling at the exploratory or conceptual level, for visual demonstration, and for educational purposes.

Gravity flow rate of solids through orifices and pipes

NASA Technical Reports Server (NTRS)

Gardner, J. F.; Smith, J. E.; Hobday, J. M.

1977-01-01

Lock-hopper systems are the most common means for feeding solids to and from coal conversion reactor vessels. The rate at which crushed solids flow by gravity through the vertical pipes and valves in lock-hopper systems affects the size of pipes and valves needed to meet the solids-handling requirements of the coal conversion process. Methods used to predict flow rates are described and compared with experimental data. Preliminary indications are that solids-handling systems for coal conversion processes are over-designed by a factor of 2 or 3.

Considerations in pharmaceutical conversion: focus on antihistamines.

PubMed

Garbus, S B; Moulton, B W; Meltzer, E O; Reich, P R; Weinreb, L F; Friedman, J A; Orland, B I

1997-04-01

The practice of pharmaceutical conversion, which encompasses three types of drug interchange (generic, brand, and therapeutic substitution), is increasing in managed care settings. Pharmaceutical conversion has numerous implications for managed care organizations, their healthcare providers, and their customers. Although drug cost may be a driving consideration in pharmaceutical conversion, a number of other considerations are of equal or greater importance in the decision-making process may affect the overall cost of patient care. Among these considerations are clinical, psychosocial, and safety issues; patient adherence; patient satisfaction; and legal implications of pharmaceutical conversion. Patient-centered care must always remain central to decisions about pharmaceutical conversion. This article discusses the issues related to, and implications of, pharmaceutical conversion utilizing the antihistamines class of drugs as the case situation.

Conversion of evanescent Lamb waves into propagating waves via a narrow aperture edge.

PubMed

Yan, Xiang; Yuan, Fuh-Gwo

2015-06-01

This paper presents a quantitative study of conversion of evanescent Lamb waves into propagating in isotropic plates. The conversion is substantiated by prescribing time-harmonic Lamb displacements/tractions through a narrow aperture at an edge of a semi-infinite plate. Complex-valued dispersion and group velocity curves are employed to characterize the conversion process. The amplitude coefficient of the propagating Lamb modes converted from evanescent is quantified based on the complex reciprocity theorem via a finite element analysis. The power flow generated into the plate can be separated into radiative and reactive parts made on the basis of propagating and evanescent Lamb waves, where propagating Lamb waves are theoretically proved to radiate pure real power flow, and evanescent Lamb waves carry reactive pure imaginary power flow. The propagating power conversion efficiency is then defined to quantitatively describe the conversion. The conversion efficiency is strongly frequency dependent and can be significant. With the converted propagating waves from evanescent, sensors at far-field can recapture some localized damage information that is generally possessed in evanescent waves and may have potential application in structural health monitoring.

Parametric modulation of thermomagnetic convection in magnetic fluids.

PubMed

Engler, H; Odenbach, S

2008-05-21

Previous theoretical investigations on thermal flow in a horizontal fluid layer have shown that the critical temperature difference, where heat transfer changes from diffusion to convective flow, depends on the frequency of a time-modulated driving force. The driving force of thermal convection is the buoyancy force resulting from the interaction of gravity and the density gradient provided by a temperature difference in the vertical direction of a horizontal fluid layer. An experimental investigation of such phenomena fails because of technical problems arising if buoyancy is to be changed by altering the temperature difference or gravitational acceleration. The possibility of influencing convective flow in a horizontal magnetic fluid layer by magnetic forces might provide us with a means to solve the problem of a time-modulated magnetic driving force. An experimental setup to investigate the dependence of the critical temperature difference on the frequency of the driving force has been designed and implemented. First results show that the time modulation of the driving force has significant influence on the strength of the convective flow. In particular a pronounced minimum in the strength of convection has been found for a particular frequency.

Ice Generation and the Heat and Mass Transfer Phenomena of Introducing Water to a Cold Bath of Brine.

PubMed

Yun, Xiao; Quarini, Giuseppe L

2017-03-13

We demonstrate a method for the study of the heat and mass transfer and of the freezing phenomena in a subcooled brine environment. Our experiment showed that, under the proper conditions, ice can be produced when water is introduced to a bath of cold brine. To make ice form, in addition to having the brine and water mix, the rate of heat transfer must bypass that of mass transfer. When water is introduced in the form of tiny droplets to the brine surface, the mode of heat and mass transfer is by diffusion. The buoyancy stops water from mixing with the brine underneath, but as the ice grows thicker, it slows down the rate of heat transfer, making ice more difficult to grow as a result. When water is introduced inside the brine in the form of a flow, a number of factors are found to influence how much ice can form. Brine temperature and concentration, which are the driving forces of heat and mass transfer, respectively, can affect the water-to-ice conversion ratio; lower bath temperatures and brine concentrations encourage more ice to form. The flow rheology, which can directly affect both the heat and mass transfer coefficients, is also a key factor. In addition, the flow rheology changes the area of contact of the flow with the bulk fluid.

Conversion economics of forest biomaterials: risk and financial analysis of CNC manufacturing

Treesearch

Camilla Abbati de Assis; Carl Houtman; Richard Phillips; E.M. Ted Bilek; Orlando J. Rojas; Lokendra Pal; Maria Soledad Peresin; Hasan Jameel; Ronalds Gonzalez

2017-01-01

Commercialization of cellulose nanocrystals (CNC) presents opportunities for a wide range of new products. Techno-economic assessments can provide insightful information for the effi cient design of conversion processes, drive cost-saving efforts, and reduce fi nancial risks. In this study, we conducted techno-economic assessments for CNC production using information...

Efficient extreme-UV-to-extreme-UV conversion by four-wave mixing with intense near-IR pulses in highly charged ion plasmas

NASA Astrophysics Data System (ADS)

Chu, Hsu-hsin; Wang, Jyhpyng

2018-05-01

Nonlinear optics in the extreme-ultraviolet (EUV) has been limited by lack of transparent media and small conversion efficiency. To overcome this problem we explore the advantage of using multiply charged ion plasmas as the interacting media between EUV and intense near-infrared (NIR) pulses. Such media are transparent to EUV and can withstand intense NIR driving pulses without damage. We calculate the third-order nonlinear polarizabilities of Ar2 + and Ar3 + ions for EUV and NIR four-wave mixing by using the well-proven Cowan code and find that the EUV-to-EUV conversion efficiency as high as 26% can be expected for practical experimental configurations using multi-terawatt NIR lasers. Such a high efficiency is possible because the driving pulse intensity can be scaled up to several orders of magnitude higher than in conventional nonlinear media, and the group-velocity and phase mismatch are insignificant at the experimental plasma densities. This effective scheme of wave mixing can be utilized for ultrafast EUV waveform measurement and control as well as wavelength conversion.

X-ray conversion efficiency of high-Z hohlraum wall materials for indirect drive ignition

NASA Astrophysics Data System (ADS)

Dewald, E. L.; Rosen, M.; Glenzer, S. H.; Suter, L. J.; Girard, F.; Jadaud, J. P.; Schein, J.; Constantin, C.; Wagon, F.; Huser, G.; Neumayer, P.; Landen, O. L.

2008-07-01

The conversion efficiency of 351nm laser light to soft x rays (0.1-5keV) was measured for Au, U, and high Z mixture "cocktails" used as hohlraum wall materials in indirect drive fusion experiments. For the spherical targets in a direct drive geometry, flattop laser pulses and laser smoothing with phase plates are employed to achieve constant and uniform laser intensities of 1014 and 1015W/cm2 over the target surface that are relevant for the future ignition experiments at the National Ignition Facility [G. H. Miller, E. I. Moses, and C. R. Wuest, Nucl. Fusion 44, 228 (2004)]. The absolute time and spectrally resolved radiation flux is measured with a multichannel soft x-ray power diagnostic. The conversion efficiency is then calculated by dividing the measured x-ray power by the incident laser power from which the measured laser backscattering losses are subtracted. After ˜0.5ns, the time resolved x-ray conversion efficiency reaches a slowly increasing plateau of 95% at 1014W/cm2 laser intensity and of 80% at 1015W/cm2. The M-band flux (2-5keV) is negligible at 1014W/cm2 reaching ˜1% of the total x-ray flux for all target materials. In contrast, the M-band flux is significant and depends on the target material at 1015W/cm2 laser intensity, reaching values between 10% of the total flux for U and 27% for Au. LASNEX simulations [G. B. Zimmerman and W. L. Kruer, Comm. Plasma Phys. Contr. Fusion 2, 51 (1975)] show good agreement in conversion efficiency and radiated spectra with data when using XSN atomic physics model and a flux limiter of 0.15, but they underestimate the generated M-band flux.

Comparative efficiency of technologies for conversion and transportation of energy resources of Russia's eastern regions to NEA countries

NASA Astrophysics Data System (ADS)

Kler, Aleksandr; Tyurina, Elina; Mednikov, Aleksandr

2018-01-01

The paper presents perspective technologies for combined conversion of fossil fuels into synthetic liquid fuels and electricity. The comparative efficiency of various process flows of conversion and transportation of energy resources of Russia's east that are aimed at supplying electricity to remote consumers is presented. These also include process flows based on production of synthetic liquid fuel.

Conversion of carbon dioxide to carbon monoxide by pulse dielectric barrier discharge plasma

NASA Astrophysics Data System (ADS)

Wang, Taobo; Liu, Hongxia; Xiong, Xiang; Feng, Xinxin

2017-01-01

The conversion of carbon dioxide (CO2) to carbon monoxide (CO) was investigated in a non-thermal plasma dielectric barrier discharge (DBD) reactor, and the effects of different process conditions on the CO2 conversion were investigated. The results showed that the increase of input power could optimize the conversion of CO2 to CO. The CO2 conversion and CO yield were negatively correlated with the gas flow rate, but there was an optimum gas flow rate, that made the CO selectivity best. The carrier gas (N2, Ar) was conducive to the conversion of CO2, and the effect of N2 as carrier gas was better than Ar. The conversion of CO2 to CO was enhanced by addition of the catalyst (5A molecular sieve).

Physics of automated driving in framework of three-phase traffic theory.

PubMed

Kerner, Boris S

2018-04-01

We have revealed physical features of automated driving in the framework of the three-phase traffic theory for which there is no fixed time headway to the preceding vehicle. A comparison with the classical model approach to automated driving for which an automated driving vehicle tries to reach a fixed (desired or "optimal") time headway to the preceding vehicle has been made. It turns out that automated driving in the framework of the three-phase traffic theory can exhibit the following advantages in comparison with the classical model of automated driving: (i) The absence of string instability. (ii) Considerably smaller speed disturbances at road bottlenecks. (iii) Automated driving vehicles based on the three-phase theory can decrease the probability of traffic breakdown at the bottleneck in mixed traffic flow consisting of human driving and automated driving vehicles; on the contrary, even a single automated driving vehicle based on the classical approach can provoke traffic breakdown at the bottleneck in mixed traffic flow.

Physics of automated driving in framework of three-phase traffic theory

NASA Astrophysics Data System (ADS)

Kerner, Boris S.

2018-04-01

We have revealed physical features of automated driving in the framework of the three-phase traffic theory for which there is no fixed time headway to the preceding vehicle. A comparison with the classical model approach to automated driving for which an automated driving vehicle tries to reach a fixed (desired or "optimal") time headway to the preceding vehicle has been made. It turns out that automated driving in the framework of the three-phase traffic theory can exhibit the following advantages in comparison with the classical model of automated driving: (i) The absence of string instability. (ii) Considerably smaller speed disturbances at road bottlenecks. (iii) Automated driving vehicles based on the three-phase theory can decrease the probability of traffic breakdown at the bottleneck in mixed traffic flow consisting of human driving and automated driving vehicles; on the contrary, even a single automated driving vehicle based on the classical approach can provoke traffic breakdown at the bottleneck in mixed traffic flow.

How we can measure the non-driving-task engagement in automated driving: Comparing flow experience and workload.

PubMed

Ko, Sang Min; Ji, Yong Gu

2018-02-01

In automated driving, a driver can completely concentrate on non-driving-related tasks (NDRTs). This study investigated the flow experience of a driver who concentrated on NDRTs and tasks that induce mental workload under conditional automation. Participants performed NDRTs under different demand levels: a balanced demand-skill level (fit condition) to induce flow, low-demand level to induce boredom, and high-demand level to induce anxiety. In addition, they performed the additional N-Back task, which artificially induces mental workload. The results showed participants had the longest reaction time when they indicated the highest flow score, and had the longest gaze-on time, road-fixation time, hands-on time, and take-over time under the fit condition. Significant differences were not observed in the driver reaction times in the fit condition and the additional N-Back task, indicating that performing NDRTs that induce a high flow experience could influence driver reaction time similar to performing tasks with a high mental workload. Copyright © 2017. Published by Elsevier Ltd.

Plasma MRI Experiments at UW-Madison

NASA Astrophysics Data System (ADS)

Flanagan, K.; Clark, M.; Desangles, V.; Siller, R.; Wallace, J.; Weisberg, D.; Forest, C. B.

2015-11-01

Experiments for driving Keplerian-like flow profiles on both the Plasma Couette Experiment Upgrade (PCX-U) and the Wisconsin Plasma Astrophysics Laboratory (WiPAL) user facility are described. Instead of driving flow at the boundaries, as is typical in many liquid metal Couette experiments, a global drive is implemented. A large radial current is drawn across a small axial field generating torque across the whole profile. This global electrically driven flow is capable of producing profiles similar to Keplerian flow. PCX-U has been purposely constructed for MRI experiments, while similar experiments on the WiPAL device show the versatility of the user facility and provide a larger plasma volume. Numerical calculations show the predicted parameter spaces for exciting the MRI in these plasmas and the equilibrium flow profiles expected. In both devices, relevant MRI parameters appear to be within reach of typical operating characteristics.

Subsonic and Supersonic shear flows in laser driven high-energy-density plasmas

NASA Astrophysics Data System (ADS)

Harding, E. C.; Drake, R. P.; Gillespie, R. S.; Grosskopf, M. J.; Kuranz, C. C.; Visco, A.; Ditmar, J. R.; Aglitskiy, Y.; Weaver, J. L.; Velikovich, A. L.; Hurricane, O. A.; Hansen, J. F.; Remington, B. A.; Robey, H. F.; Bono, M. J.; Plewa, T.

2009-05-01

Shear flows arise in many high-energy-density (HED) and astrophysical systems, yet few laboratory experiments have been carried out to study their evolution in these extreme environments. Fundamentally, shear flows can initiate mixing via the Kelvin-Helmholtz (KH) instability and may eventually drive a transition to turbulence. We present two dedicated shear flow experiments that created subsonic and supersonic shear layers in HED plasmas. In the subsonic case the Omega laser was used to drive a shock wave along a rippled plastic interface, which subsequently rolled-upped into large KH vortices. In the supersonic shear experiment the Nike laser was used to drive Al plasma across a low-density foam surface also seeded with a ripple. Unlike the subsonic case, detached shocks developed around the ripples in response to the supersonic Al flow.

Technique for measuring gas conversion factors

NASA Technical Reports Server (NTRS)

Singh, J. J.; Sprinkle, D. R. (Inventor)

1985-01-01

A method for determining hydrocarbon conversion factors for a flowmeter. A mixture of air, O2 and C sub x H sub y is burned and the partial paressure of O2 in the resulting gas is forced to equal the partial pressure of O2 in air. The flowrate of O2 flowing into the mixture is measured by flowmeter and the flowrate of C sub x H sub y flowing into the mixture is measured by the flowmeter conversion factor is to be determined. These measured values are used to calculate the conversion factor.

Text messaging during simulated driving.

PubMed

Drews, Frank A; Yazdani, Hina; Godfrey, Celeste N; Cooper, Joel M; Strayer, David L

2009-10-01

This research aims to identify the impact of text messaging on simulated driving performance. In the past decade, a number of on-road, epidemiological, and simulator-based studies reported the negative impact of talking on a cell phone on driving behavior. However, the impact of text messaging on simulated driving performance is still not fully understood. Forty participants engaged in both a single task (driving) and a dual task (driving and text messaging) in a high-fidelity driving simulator. Analysis of driving performance revealed that participants in the dual-task condition responded more slowly to the onset of braking lights and showed impairments in forward and lateral control compared with a driving-only condition. Moreover, text-messaging drivers were involved in more crashes than drivers not engaged in text messaging. Text messaging while driving has a negative impact on simulated driving performance. This negative impact appears to exceed the impact of conversing on a cell phone while driving. The results increase our understanding of driver distraction and have potential implications for public safety and device development.

Reversible Gene Drive Mechanism Utilizing Trana Inactivating Paramutatlons In Insects (paramutale 0.9)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drocco, Jeffery A.

The paramutate software package Is a tool to calculate the genotyplc and phenotyplc propagation of a gene drive that can be silenced with a homologuus trans-Inactivating panmutatlon, ln dlptera or other species with a slmUar-acttng pl RNA system/Plwi pathway. Method of SolaUon: paramutate uses rults of Mendelian, gene drive (I.e.. stimulated conversion), and maternal Inheritance to compute the propaptlon of a notional gene drive construct and Its trans-lnactlvat1n1 paramutatlon, throu1b a panmlctlc, fixed-size population reproducing In synchronous generations.

Induced charge electroosmosis micropumps using arrays of Janus micropillars.

PubMed

Paustian, Joel S; Pascall, Andrew J; Wilson, Neil M; Squires, Todd M

2014-09-07

We report on a microfluidic AC-driven electrokinetic pump that uses Induced Charge Electro-Osmosis (ICEO) to generate on-chip pressures. ICEO flows occur when a bulk electric field polarizes a metal object to induce double layer formation, then drives electroosmotic flow. A microfabricated array of metal-dielectric Janus micropillars breaks the symmetry of ICEO flow, so that an AC electric field applied across the array drives ICEO flow along the length of the pump. When pumping against an external load, a pressure gradient forms along the pump length. The design was analyzed theoretically with the reciprocal theorem. The analysis reveals a maximum pressure and flow rate that depend on the ICEO slip velocity and micropillar geometry. We then fabricate and test the pump, validating our design concept by demonstrating non-local pressure driven flow using local ICEO slip flows. We varied the voltage, frequency, and electrolyte composition, measuring pump pressures of 15-150 Pa. We use the pump to drive flows through a high-resistance microfluidic channel. We conclude by discussing optimization routes suggested by our theoretical analysis to enhance the pump pressure.

Characterizing Hohlraum Plasma Conditions at the National Ignition Facility (NIF) Using X-ray Spectroscopy

NASA Astrophysics Data System (ADS)

Barrios, Maria Alejandra

2015-11-01

Improved hohlraums will have a significant impact on increasing the likelihood of indirect drive ignition at the NIF. In indirect-drive Inertial Confinement Fusion (ICF), a high-Z hohlraum converts laser power into a tailored x-ray flux that drives the implosion of a spherical capsule filled with D-T fuel. The x-radiation drive to capsule coupling sets the velocity, adiabat, and symmetry of the implosion. Previous experiments in gas-filled hohlraums determined that the laser-hohlraum energy coupling is 20-25% less than modeled, therefore identifying energy loss mechanisms that reduce the efficacy of the hohlraum drive is central to improving implosion performance. Characterizing the plasma conditions, particularly the plasma electron temperature (Te) , is critical to understanding mechanism that affect the energy coupling such as the laser plasma interactions (LPI), hohlraum x-ray conversion efficiency, and dynamic drive symmetry. The first Te measurements inside a NIF hohlraum, presented here, were achieved using K-shell X-ray spectroscopy of an Mn-Co tracer dot. The dot is deposited on a thin-walled CH capsule, centered on the hohlraum symmetry axis below the laser entrance hole (LEH) of a bottom-truncated hohlraum. The hohlraum x-ray drive ablates the dot and causes it to flow upward, towards the LEH, entering the hot laser deposition region. An absolutely calibrated streaked spectrometer with a line of sight into the LEH records the temporal history of the Mn and Co X-ray emission. The measured (interstage) Lyα/ Heα line ratios for Co and Mn and the Mn-Heα/Co-Heα isoelectronic line ratio are used to infer the local plasma Te from the atomic physics code SCRAM. Time resovled x-ray images perpendicular to the hohlraum axis record the dot expansion and trajectory into the LEH region. The temporal evolution of the measured Te and dot trajectory are compared with simulations from radiation-hydrodynamic codes. This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344.

Alfven resonance mode conversion in the Phaedrus-T current drive experiments: Modelling and density fluctuations measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vukovic, M.; Harper, M.; Breun, R.

1995-12-31

Current drive experiments on the Phaedrus-T tokamak performed with a low field side two-strap fast wave antenna at frequencies below {omega}{sub cH} show loop volt drops of up to 30% with strap phasing (0, {pi}/2). RF induced density fluctuations in the plasma core have also been observed with a microwave reflectometer. It is believed that they are caused by kinetic Alfven waves generated by mode conversion of fast waves at the Alfven resonance. Correlation of the observed density fluctuations with the magnitude of the {Delta}V{sub loop} suggest that the {Delta}V{sub loop} is attributable to current drive/heating due to mode convertedmore » kinetic Alfven waves. The toroidal cold plasma wave code LION is used to model the Alfven resonance mode conversion surfaces in the experiments while the cylindrical hot plasma kinetic wave code ISMENE is used to model the behavior of kinetic Alfven waves at the Alfven resonance location. Initial results obtained from limited density, magnetic field, antenna phase, and impurity scans show good agreement between the RF induced density fluctuations and the predicted behavior of the kinetic Alfven waves. Detailed comparisons between the density fluctuations and the code predictions are presented.« less

Forced Reconnection in the Near Magnetotail: Onset and Energy Conversion in PIC and MHD Simulations

NASA Technical Reports Server (NTRS)

Birn, J.; Hesse, Michael

2014-01-01

Using two-dimensional particle-in-cell (PIC) together with magnetohydrodynamic (MHD) Q1 simulations of magnetotail dynamics, we investigate the evolution toward onset of reconnection and the subsequent energy transfer and conversion. In either case, reconnection onset is preceded by a driven phase, during which magnetic flux is added to the tail at the high-latitude boundaries, followed by a relaxation phase, during which the configuration continues to respond to the driving. The boundary deformation leads to the formation of thin embedded current sheets, which are bifurcated in the near tail, converging to a single sheet farther out in the MHD simulations. The thin current sheets in the PIC simulation are carried by electrons and are associated with a strong perpendicular electrostatic field, which may provide a connection to parallel potentials and auroral arcs and an ionospheric signal even prior to the onset of reconnection. The PIC simulation very well satisfies integral entropy conservation (intrinsic to ideal MHD) during this phase, supporting ideal ballooning stability. Eventually, the current intensification leads to the onset of reconnection, the formation and ejection of a plasmoid, and a collapse of the inner tail. The earthward flow shows the characteristics of a dipolarization front: enhancement of Bz, associated with a thin vertical electron current sheet in the PIC simulation. Both MHD and PIC simulations show a dominance of energy conversion from incoming Poynting flux to outgoing enthalpy flux, resulting in heating of the inner tail. Localized Joule dissipation plays only a minor role.

Reducing the net torque and flow ripple effects of multiple hydraulic piston motor drives

NASA Technical Reports Server (NTRS)

Bartos, R. D.

1992-01-01

The torque and flow ripple effects which result when multiple hydraulic motors are used to drive a single motion of a mechanical device can significantly affect the way in which the device performs. This article presents a mathematical model describing the torque and flow ripple effects of a bent-axis hydraulic piston motor. The model is used to show how the ripple magnitude can be reduced when multiple motors are used to drive a motion. A discussion of the hydraulic servo system of the 70-m antennas located with the Deep Space Network is included to demonstrate the application of the concepts presented.

Phoning while driving I: a review of epidemiological, psychological, behavioural and physiological studies.

PubMed

Collet, C; Guillot, A; Petit, C

2010-05-01

The impact of cell (mobile) phone use on driving performance has been widely questioned for 20 years. This paper reviews the literature to evaluate the extent to which phoning may impact behaviour with a risk to affect safety. After analysing epidemiological studies that give an overview of cell phone use, this paper examines the experimental results and focuses on variables showing that driving is impacted by holding a mobile-phone conversation. Information processing (e.g. reaction time and detection rate of cues related to driving information) and variables associated with vehicle control (e.g. lane-keeping, headway and vehicle speed) seem the most relevant. Although less studied than behavioural indices, physiological data give information about the supplementary potential strain that the driver may undergo under dual-task conditions. This first part of the review highlights common findings, questionable results and differences among studies, which originate from specific experimental designs with particular dependent variables, i.e. self-report, behavioural and physiological indicators. Finally, how drivers try to compensate for the additional load brought by phone use is described. STATEMENT OF RELEVANCE: The two papers review the influence of mobile-phone use on driving performance. While there is ample evidence that this dual task is likely to increase the risk of car crash, the review analyses the variables eliciting detrimental conditions and, conversely, those that may preserve acceptable conditions for safety, close to usual driving. The decision of answering or initiating a cell phone call while driving depends upon the complex interaction among several variables, including driving conditions and driver's own characteristics. In addition, this decision remains under driver's awareness of being able or not to manage the two tasks simultaneously.

How are Inner Hair Cells Stimulated? Evidence for multiple mechanical drives

PubMed Central

Guinan, John J.

2013-01-01

Recent studies indicate that the gap over outer hair cells (OHCs) between the reticular lamina (RL) and the tectorial membrane (TM) varies cyclically during low-frequency sounds. Variation in the RL-TM gap produces radial fluid flow in the gap that can drive inner hair cell (IHC) stereocilia. Analysis of RL-TM gap changes reveals three IHC drives in addition to classic SHEAR. For upward basilar-membrane (BM) motion, IHC stereocilia are deflected in the excitatory direction by SHEAR and OHC-MOTILITY, but in the inhibitory direction by TM-PUSH and CILIA-SLANT. Upward BM motion causes OHC somatic contraction which tilts the RL, compresses the RL-TM gap over IHCs and expands the RL-TM gap over OHCs, thereby producing an outward (away from the IHCs) radial fluid flow which is the OHC-MOTILITY drive. For upward BM motion, the force that moves the TM upward also compresses the RL-TM gap over OHCs causing inward radial flow past IHCs which is the TM-PUSH drive. Motions that produce large tilting of OHC stereocilia squeeze the supra-OHC RL-TM gap and caused inward radial flow past IHCs which is the CILIA-SLANT drive. Combinations of these drives explain: (1) the reversal at high sound levels of auditory nerve (AN) initial peak (ANIP) responses to clicks, and medial olivocochlear (MOC) inhibition of ANIP responses below, but not above, the ANIP reversal, (2) dips and phase reversals in AN responses to tones in cats and chinchillas, (3) hypersensitivity and phase reversals in tuning-curve tails after OHC ablation, and (4) MOC inhibition of tail-frequency AN responses. The OHC-MOTILITY drive provides another mechanism, in addition to BM motion amplification, that uses active processes to enhance the output of the cochlea. The ability of these IHC drives to explain previously anomalous data provides strong, although indirect, evidence that these drives are significant and presents a new view of how the cochlea works at frequencies below 3 kHz. PMID:22959529

Gene conversion and positive selection driving the evolution of the Caenorhabditis ssp. ZIM/HIM-8 protein family.

PubMed

Liu, Qingpo

2009-03-01

In C. elegans, four C2H2 zinc-finger proteins (ZIM-1, ZIM-2, ZIM-3, and HIM-8), which are arranged in tandem, mediate chromosome-specific pairing and synapsis during meiosis. The zim/him-8 genes from three Caenorhabditis species were contrasted in an effort to investigate the mechanisms driving their evolution. Here it is shown that the preservation of higher degree of sequence similarity in the N-terminal portion, particularly in several regions within the second exon between paralogous zim genes (especially between zim-1 and zim-3), is due to independent interparalogue gene conversions. However, the evolutionary force is not uniformly strong across species. The present data reveal that more frequent gene conversion events have occurred in C. elegans, whereas only gene conversions between zim-1 and zim-3 are detected in C. remanei. Although gene conversions are predicted to be present among zim-1, zim-2, and zim-3 in C. briggsae, the conversion tracts between zim-1/zim-2 and zim-2/zim-3 are very short. Moreover, positive selection analysis was performed on the basis of the significantly discordant phylogenies reconstructed using the N- and C-terminal sequences, respectively. Several codon sites located in the regions that are supposed not to have experienced gene conversions are predicted to be under the influence of positive selection. In comparison, stronger positive selection has acted on the C-terminal region relative to the N-terminal region. Thus, the zim/him-8 genes that evolve concertedly have also been shown to undergo adaptive diversifying selection.

The Neural Correlates of Driving Performance Identified Using Positron Emission Tomography

ERIC Educational Resources Information Center

Horikawa, E.; Okamura, N.; Tashiro, M.; Sakurada, Y.; Maruyama, M.; Arai, H.; Yamaguchi, K.; Sasaki, H.; Yanai, K.; Itoh, M.

2005-01-01

Driving is a complex behavior involving multiple cognitive domains. To identify neural correlates of driving performance, [^1^5O]H"2O positron emission tomography was performed using a simulated driving task. Compared with the resting condition, simulated driving increased regional cerebral blood flow (rCBF) in the cerebellum, occipital, and…

Test Results from a Direct Drive Gas Reactor Simulator Coupled to a Brayton Power Conversion Unit

NASA Technical Reports Server (NTRS)

Hervol, David S.; Briggs, Maxwell H.; Owen, Albert K.; Bragg-Sitton, Shannon M.; Godfroy, Thomas J.

2010-01-01

Component level testing of power conversion units proposed for use in fission surface power systems has typically been done using relatively simple electric heaters for thermal input. These heaters do not adequately represent the geometry or response of proposed reactors. As testing of fission surface power systems transitions from the component level to the system level it becomes necessary to more accurately replicate these reactors using reactor simulators. The Direct Drive Gas-Brayton Power Conversion Unit test activity at the NASA Glenn Research Center integrates a reactor simulator with an existing Brayton test rig. The response of the reactor simulator to a change in Brayton shaft speed is shown as well as the response of the Brayton to an insertion of reactivity, corresponding to a drum reconfiguration. The lessons learned from these tests can be used to improve the design of future reactor simulators which can be used in system level fission surface power tests.

Data-Driven Leadership: Determining Your Indicators and Building Your Dashboards

ERIC Educational Resources Information Center

Copeland, Mo

2016-01-01

For years, schools have tended to approach budgets with some basic assumptions and aspirations and general wish lists but with scant data to drive the budget conversation. Suppose there were a better way? What if the conversation started with a review of the last five to ten years of data on three key mission- and strategy-driven indicators:…

Measurement of blood flow from an assist ventricle by computation of pneumatic driving parameters.

PubMed

Qian, K X

1992-03-01

The measurement of blood flow from an assist ventricle is important but sometimes difficult in artificial heart experiments. Along with the development of a pneumatic cylinder-piston driver coupled with a ventricular assist device, a simplified method for measuring pump flow was established. From driving parameters such as the piston (or cylinder) displacement and air pressure, the pump flow could be calculated by the use of the equation of state for an ideal gas. The results of this method are broadly in agreement with electromagnetic and Doppler measurements.

The Mekong's future flows under multiple driving factors: How future climate change, hydropower developments and irrigation expansion drive hydrological changes?

NASA Astrophysics Data System (ADS)

Hoang, L. P.; van Vliet, M. T. H.; Lauri, H.; Kummu, M.; Koponen, J.; Supit, I.; Leemans, R.; Kabat, P.; Ludwig, F.

2016-12-01

The Mekong River's flows and water resources are in many ways essential for sustaining economic growths, flood security of about 70 million people and biodiversity in one of the world's most ecologically productive wetland systems. The river's hydrological cycle, however, are increasingly perturbed by climate change, large-scale hydropower developments and rapid irrigated land expansions. This study presents an integrated impact assessment to characterize and quantify future hydrological changes induced by these driving factors, both separately and combined. We have integrated a crop simulation module and a hydropower dam module into a distributed hydrological model (VMod) and simulated the Mekong's hydrology under multiple climate change and development scenarios. Our results show that the Mekong's hydrological regime will experience substantial changes caused by the considered factors. Magnitude-wise, hydropower dam developments exhibit the largest impacts on river flows, with projected higher flows (up to +35%) during the dry season and lower flows (up to -44%) during the wet season. Annual flow changes caused by the dams, however, are relatively marginal. In contrast to this, climate change is projected to increase the Mekong's annual flows (up to +16%) while irrigated land expansions result in annual flow reductions (-1% to -3%). Combining the impacts of these three drivers, we found that river flow changes, especially those at the monthly scale, largely differ from changes under the individual driving factors. This is explained by large differences in impacts' magnitudes and contrasting impacts' directions for the individual drivers. We argue that the Mekong's future flows are likely driven by multiple factors and thus advocate for integrated assessment approaches and tools that support proper considerations of these factors and their interplays.

Self-actuated shutdown-system development: system response-analysis status

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deane, N.A.; Gregoire, K.E.; Tatsumi, J.T.

1980-09-01

This report provides a preliminary evaluation of the SASS response time requirements for the safe shutdown earthquake (SSE), the flow coastdown (FCD), and two transient overpower (TOP) events. The driving functions for the SSE are a 20 cent step reactivity insertion with a +- 60 cent oscillation super imposed for 10 seconds combined with a flow coastdown defined by F/F/sub (0)/ = 1/(1+.2788t). The driving function of the FCD is just the relative flow curve defined above for the SSE. The TOP event driving function represents a control rod runout to a total of 60 cents at ramp rates ofmore » .76 cents/s and 6.1 cents/s. 3 figures.« less

Transport of particles and microorganisms in microfluidic channels using rectified ac electro-osmotic flow

PubMed Central

Wu, Wen-I; Selvaganapathy, P. Ravi; Ching, Chan Y.

2011-01-01

A new method is demonstrated to transport particles, cells, and other microorganisms using rectified ac electro-osmotic flows in open microchannels. The rectified flow is obtained by synchronous zeta potential modulation with the driving potential in the microchannel. Experiments were conducted to transport both neutral, charged particles, and microorganisms of various sizes. A maximum speed of 50 μm∕s was obtained for 8 μm polystyrene beads, without any electrolysis, using a symmetrical square waveform driving electric field of 5 V∕mm at 10 Hz and a 360 V gate potential with its polarity synchronized with the driving potential (phase lag=0°). PMID:21522497

Alternative Fuels Data Center: Propane

Science.gov Websites

they work, and find information about vehicle availability, conversions, emissions, maintenance, and Fuel Prices Conserve Fuel Idle Reduction Parts & Equipment Maintenance Driving Behavior Fleet

Hydrologic regimes as potential drivers of morphologic divergence in fish

USGS Publications Warehouse

Bruckerhoff, Lindsey; Magoulick, Daniel D.

2017-01-01

Fishes often exhibit phenotypic divergence across gradients of abiotic and biotic selective pressures. In streams, many of the known selective pressures driving phenotypic differentiation are largely influenced by hydrologic regimes. Because flow regimes drive so many attributes of lotic systems, we hypothesized fish exhibit phenotypic divergence among streams with different flow regimes. We used a comparative field study to investigate the morphological divergence of Campostoma anomalom (central stonerollers) among streams characterized by highly variable, intermittent flow regimes and streams characterized by relatively stable, groundwater flow regimes. We also conducted a mesocosm experiment to compare the plastic effects of one component of flow regimes, water velocity, on morphology of fish from different flow regimes. We observed differences in shape between flow regimes likely driven by differences in allometric growth patterns. Although we observed differences in morphology across flow regimes in the field, C. anomalum did not exhibit morphologic plasticity in response to water velocity alone. This study contributes to the understanding of how complex environmental factors drive phenotypic divergence and may provide insight into the evolutionary consequences of disrupting natural hydrologic patterns, which are increasingly threatened by climate change and anthropogenic alterations.

20 years of research on the Alcator C-Mod tokamaka)

NASA Astrophysics Data System (ADS)

Greenwald, M.; Bader, A.; Baek, S.; Bakhtiari, M.; Barnard, H.; Beck, W.; Bergerson, W.; Bespamyatnov, I.; Bonoli, P.; Brower, D.; Brunner, D.; Burke, W.; Candy, J.; Churchill, M.; Cziegler, I.; Diallo, A.; Dominguez, A.; Duval, B.; Edlund, E.; Ennever, P.; Ernst, D.; Faust, I.; Fiore, C.; Fredian, T.; Garcia, O.; Gao, C.; Goetz, J.; Golfinopoulos, T.; Granetz, R.; Grulke, O.; Hartwig, Z.; Horne, S.; Howard, N.; Hubbard, A.; Hughes, J.; Hutchinson, I.; Irby, J.; Izzo, V.; Kessel, C.; LaBombard, B.; Lau, C.; Li, C.; Lin, Y.; Lipschultz, B.; Loarte, A.; Marmar, E.; Mazurenko, A.; McCracken, G.; McDermott, R.; Meneghini, O.; Mikkelsen, D.; Mossessian, D.; Mumgaard, R.; Myra, J.; Nelson-Melby, E.; Ochoukov, R.; Olynyk, G.; Parker, R.; Pitcher, S.; Podpaly, Y.; Porkolab, M.; Reinke, M.; Rice, J.; Rowan, W.; Schmidt, A.; Scott, S.; Shiraiwa, S.; Sierchio, J.; Smick, N.; Snipes, J. A.; Snyder, P.; Sorbom, B.; Stillerman, J.; Sung, C.; Takase, Y.; Tang, V.; Terry, J.; Terry, D.; Theiler, C.; Tronchin-James, A.; Tsujii, N.; Vieira, R.; Walk, J.; Wallace, G.; White, A.; Whyte, D.; Wilson, J.; Wolfe, S.; Wright, G.; Wright, J.; Wukitch, S.; Zweben, S.

2014-11-01

The object of this review is to summarize the achievements of research on the Alcator C-Mod tokamak [Hutchinson et al., Phys. Plasmas 1, 1511 (1994) and Marmar, Fusion Sci. Technol. 51, 261 (2007)] and to place that research in the context of the quest for practical fusion energy. C-Mod is a compact, high-field tokamak, whose unique design and operating parameters have produced a wealth of new and important results since it began operation in 1993, contributing data that extends tests of critical physical models into new parameter ranges and into new regimes. Using only high-power radio frequency (RF) waves for heating and current drive with innovative launching structures, C-Mod operates routinely at reactor level power densities and achieves plasma pressures higher than any other toroidal confinement device. C-Mod spearheaded the development of the vertical-target divertor and has always operated with high-Z metal plasma facing components—approaches subsequently adopted for ITER. C-Mod has made ground-breaking discoveries in divertor physics and plasma-material interactions at reactor-like power and particle fluxes and elucidated the critical role of cross-field transport in divertor operation, edge flows and the tokamak density limit. C-Mod developed the I-mode and the Enhanced Dα H-mode regimes, which have high performance without large edge localized modes and with pedestal transport self-regulated by short-wavelength electromagnetic waves. C-Mod has carried out pioneering studies of intrinsic rotation and demonstrated that self-generated flow shear can be strong enough in some cases to significantly modify transport. C-Mod made the first quantitative link between the pedestal temperature and the H-mode's performance, showing that the observed self-similar temperature profiles were consistent with critical-gradient-length theories and followed up with quantitative tests of nonlinear gyrokinetic models. RF research highlights include direct experimental observation of ion cyclotron range of frequency (ICRF) mode-conversion, ICRF flow drive, demonstration of lower-hybrid current drive at ITER-like densities and fields and, using a set of novel diagnostics, extensive validation of advanced RF codes. Disruption studies on C-Mod provided the first observation of non-axisymmetric halo currents and non-axisymmetric radiation in mitigated disruptions. A summary of important achievements and discoveries are included.

Influence of intermittent stream connectivity on water quality and salmonid survivorship.

NASA Astrophysics Data System (ADS)

Hildebrand, J.; Woelfle-Erskine, C. A.; Larsen, L.

2014-12-01

Anthropogenic stress and climate change are causing an increasing number of California streams to become intermittent and are driving earlier and more severe summertime drying. The extent to which emerging water conservation alternatives impact flows or habitat quality (e.g. temperature, DO) for salmonids remains poorly understood. Here, we investigate the proximal drivers of salmonid mortality over a range of connectivity conditions during summertime intermittency in Salmon Creek watershed, Sonoma County, CA. Through extensive sampling in paired subwatersheds over a period of two years, we tested the hypothesis that accumulation of readily bioavailable DOC in poorly flushed pools drives DO decline associated with loss of salmonids. We then traced the origin and flow pathways of DOC throughout the watershed using Parallel Factor Analysis (PARAFAC). We obtained samples for DOC and stable isotope analyses at monthly intervals from 20 piezometers and surface water in the study reaches and from private wells and springs distributed throughout the watersheds. We also obtained in situ DO, conductivity and pH readings within stream study reaches. We determined DOC quality by SUVA (specific UV absorbance) and fluorescence index. We calculated stream metabolism rates using the single station method. In pools instrumented with DO sensors, we compared changing DOC quality during the summer months to changes in DO concentrations and stream metabolism. Our results show that the duration of complete disconnection of pools during the summer months and stream metabolic rates are positively correlated with salmonid mortality. Furthermore, our results indicate that salmonid mortality is greatest in disconnected pools with low DOC fluorescence indices and high SUVA values, indicative of terrestrially derived DOC and little or no groundwater inflow. Conversely low salmonid mortality was found in disconnected pools with high fluorescence index and low SUVA, indicative of microbially derived DOC. These pools showed clear signs of hyporheic inflow during summertime drying despite complete surficial disconnection. PARAFAC analysis pinpointed groundwater sources of hyporheic flow in the watershed, suggesting that targeted aquifer recharge may contribute to salmonid recovery by augmenting flow in summer refugia.

The mean Evershed flow

NASA Astrophysics Data System (ADS)

Hu, W.-R.

1984-09-01

The paper gives a theoretical analysis of the overall characteristics of the Evershed flow (one of the main features of sunspots), with particular attention given to its outward flow from the umbra in the photosphere, reaching a maximum somewhere in the penumbra, and decreasing rapidly further out, and its inward flow of a comparable magnitude in chromosphere. Because the inertial force of the flow is small, the relevant dynamic process can be divided into a base state and a perturbation. The base-state solution yields the equilibrium relations between the pressure gradient, the Lorentz force, and gravity, and the flow law. The perturbation describes the force driving the Evershed flow. Since the pressure gradient in the base state is already in equilibrium with the Lorentz force and the gravity, the driving force of the mean Evershed flow is small.

Investigation of Multiscale and Multiphase Flow, Transport and Reaction in Heavy Oil Recovery Processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yortsos, Yanis C.

In this report, the thrust areas include the following: Internal drives, vapor-liquid flows, combustion and reaction processes, fluid displacements and the effect of instabilities and heterogeneities and the flow of fluids with yield stress. These find respective applications in foamy oils, the evolution of dissolved gas, internal steam drives, the mechanics of concurrent and countercurrent vapor-liquid flows, associated with thermal methods and steam injection, such as SAGD, the in-situ combustion, the upscaling of displacements in heterogeneous media and the flow of foams, Bingham plastics and heavy oils in porous media and the development of wormholes during cold production.

High Performance Artificial Muscles Using Nanofiber and Hybrid Yarns

DTIC Science & Technology

2015-07-14

provide 3.2% energy conversion efficiency (twice that of our CNT fiber muscles and 10X that of conducting polymer muscles ). They maintain stroke without...rubber dielectric muscle layer in twisted fiber drives torsional actuation. (2) One hundred times higher torsional stroke per muscle length...artificial muscles that provide giant stroke, fast response, high force generation, and long cycle life while optimizing energy conversion efficiencies

Continuous esterification to produce biodiesel by SPES/PES/NWF composite catalytic membrane in flow-through membrane reactor: experimental and kinetic studies.

PubMed

Shi, Wenying; He, Benqiao; Cao, Yuping; Li, Jianxin; Yan, Feng; Cui, Zhenyu; Zou, Zhiqun; Guo, Shiwei; Qian, Xiaomin

2013-02-01

A novel composite catalytic membrane (CCM) was prepared from sulfonated polyethersulfone (SPES) and polyethersulfone (PES) blend supported by non-woven fabrics, as a heterogeneous catalyst to produce biodiesel from continuous esterification of oleic acid with methanol in a flow-through mode. A kinetic model of esterification was established based on a plug-flow assumption. The effects of the CCM structure (thickness, area, porosity, etc.), reaction temperature and the external and internal mass transfer resistances on esterification were investigated. The results showed that the CCM structure had a significant effect on the acid conversion. The external mass transfer resistance could be neglected when the flow rate was over 1.2 ml min(-1). The internal mass transfer resistance impacted on the conversion when membrane thickness was over 1.779 mm. An oleic acid conversion kept over 98.0% for 500 h of continuous running. The conversions obtained from the model are in good agreement with the experimental data. Copyright © 2012 Elsevier Ltd. All rights reserved.

The groundwater subsidy to vegetation: groundwater exchanges between landcover patches

NASA Astrophysics Data System (ADS)

Steven, L. I.; Gimenez, R.; Jobbagy, E. G.

2015-12-01

The Gran Chaco is a hot, dry plain, that spans over 60 million hectares across Bolivia, Paraguay, Brazil and Argentina. It supports high biodiversity in its dry forest and savannahs, but is rapidly being converted to agriculture in response to growing soy demand and technology including genetic modification and zero-till, that has made cultivation in drier landscapes more viable. Under natural conditions, the deep-rooted, native vegetation of the Chaco effectively captured all rainfall for evapotranspiration resulting in near zero groundwater recharge under the dry forest. Conversion to shallower rooted soy and corn, combined with the fallow period prior to the growing season, reduces evapotranspiration and allows some water to percolate through the root zone and recharge the groundwater system. When this groundwater recharge occurs, it creates groundwater mounding and a hydraulic gradient that drives flow to adjacent landcover patches where recharge does not occur. As the watertable rises, groundwater becomes available to the deep-rooted, dry forest vegetation. We develop a soil and groundwater flow model to simulate infiltration, percolation, evaporation, rootwater uptake, groundwater recharge and the lateral transfer of water between adjacent landcover patches to quantify this groundwater subsidy from converted agricultural lands to remnant patches of dry forest.

New particle formation and growth from methanesulfonic acid, trimethylamine and water.

PubMed

Chen, Haihan; Ezell, Michael J; Arquero, Kristine D; Varner, Mychel E; Dawson, Matthew L; Gerber, R Benny; Finlayson-Pitts, Barbara J

2015-05-28

New particle formation from gas-to-particle conversion represents a dominant source of atmospheric particles and affects radiative forcing, climate and human health. The species involved in new particle formation and the underlying mechanisms remain uncertain. Although sulfuric acid is commonly recognized as driving new particle formation, increasing evidence suggests the involvement of other species. Here we study particle formation and growth from methanesulfonic acid, trimethylamine and water at reaction times from 2.3 to 32 s where particles are 2-10 nm in diameter using a newly designed and tested flow system. The flow system has multiple inlets to facilitate changing the mixing sequence of gaseous precursors. The relative humidity and precursor concentrations, as well as the mixing sequence, are varied to explore their effects on particle formation and growth in order to provide insight into the important mechanistic steps. We show that water is involved in the formation of initial clusters, greatly enhancing their formation as well as growth into detectable size ranges. A kinetics box model is developed that quantitatively reproduces the experimental data under various conditions. Although the proposed scheme is not definitive, it suggests that incorporating such mechanisms into atmospheric models may be feasible in the near future.

Conversion of Low-Flow Priapism to High-Flow State Using T-Shunt with Tunneling.

PubMed

Mistry, Neil A; Tadros, Nicholas N; Hedges, Jason C

2017-01-01

Introduction . The three types of priapism are stuttering, arterial (high-flow, nonischemic), and venoocclusive (low-flow, ischemic). These are usually distinct entities and rarely occur in the same patient. T-shunts and other distal shunts are frequently combined with tunneling, but a seldom recognized potential complication is conversion to a high-flow state. Case Presentation . We describe 2 cases of men who presented with low-flow priapism episodes that were treated using T-shunts with tunneling that resulted with both men having recurrent erections shortly after surgery that were found to be consistent with high-flow states. Case 1 was a 33-year-old male with sickle cell anemia and case 2 was a 24-year-old male with idiopathic thrombocytopenic purpura. In both cases the men were observed over several weeks and both men returned to normal erectile function. Conclusions . Historically, proximal shunts were performed only in cases when distal shunts failed and carry a higher risk of serious complications. T-shunts and other distal shunts combined with tunneling are being used more frequently in place of proximal shunts. These cases illustrate how postoperative erections after T-shunts with tunneling can signify a conversion from low-flow to high-flow states and could potentially be misdiagnosed as an operative failure.

Noise fluctuations and drive dependence of the skyrmion Hall effect in disordered systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reichhardt, Charles; Olson Reichhardt, Cynthia Jane

Using a particle-based simulation model, we show that quenched disorder creates a drive-dependent skyrmion Hall effect as measured by the change in the ratiomore » $$R={V}_{\\perp }/{V}_{| | }$$ of the skyrmion velocity perpendicular (V ⊥) and parallel ($${V}_{| | }$$) to an external drive. R is zero at depinning and increases linearly with increasing drive, in agreement with recent experimental observations. At sufficiently high drives where the skyrmions enter a free flow regime, R saturates to the disorder-free limit. In addition, this behavior is robust for a wide range of disorder strengths and intrinsic Hall angle values, and occurs whenever plastic flow is present. For systems with small intrinsic Hall angles, we find that the Hall angle increases linearly with external drive, as also observed in experiment. In the weak pinning regime where the skyrmion lattice depins elastically, R is nonlinear and the net direction of the skyrmion lattice motion can rotate as a function of external drive. We show that the changes in the skyrmion Hall effect correlate with changes in the power spectrum of the skyrmion velocity noise fluctuations. The plastic flow regime is associated with $1/f$ noise, while in the regime in which R has saturated, the noise is white with a weak narrow band signal, and the noise power drops by several orders of magnitude. Finally, at low drives, the velocity noise in the perpendicular and parallel directions is of the same order of magnitude, while at intermediate drives the perpendicular noise fluctuations are much larger.« less

Noise fluctuations and drive dependence of the skyrmion Hall effect in disordered systems

DOE PAGES

Reichhardt, Charles; Olson Reichhardt, Cynthia Jane

2016-09-29

Using a particle-based simulation model, we show that quenched disorder creates a drive-dependent skyrmion Hall effect as measured by the change in the ratiomore » $$R={V}_{\\perp }/{V}_{| | }$$ of the skyrmion velocity perpendicular (V ⊥) and parallel ($${V}_{| | }$$) to an external drive. R is zero at depinning and increases linearly with increasing drive, in agreement with recent experimental observations. At sufficiently high drives where the skyrmions enter a free flow regime, R saturates to the disorder-free limit. In addition, this behavior is robust for a wide range of disorder strengths and intrinsic Hall angle values, and occurs whenever plastic flow is present. For systems with small intrinsic Hall angles, we find that the Hall angle increases linearly with external drive, as also observed in experiment. In the weak pinning regime where the skyrmion lattice depins elastically, R is nonlinear and the net direction of the skyrmion lattice motion can rotate as a function of external drive. We show that the changes in the skyrmion Hall effect correlate with changes in the power spectrum of the skyrmion velocity noise fluctuations. The plastic flow regime is associated with $1/f$ noise, while in the regime in which R has saturated, the noise is white with a weak narrow band signal, and the noise power drops by several orders of magnitude. Finally, at low drives, the velocity noise in the perpendicular and parallel directions is of the same order of magnitude, while at intermediate drives the perpendicular noise fluctuations are much larger.« less

A Simple Hydraulic Analog Model of Oxidative Phosphorylation.

PubMed

Willis, Wayne T; Jackman, Matthew R; Messer, Jeffrey I; Kuzmiak-Glancy, Sarah; Glancy, Brian

2016-06-01

Mitochondrial oxidative phosphorylation is the primary source of cellular energy transduction in mammals. This energy conversion involves dozens of enzymatic reactions, energetic intermediates, and the dynamic interactions among them. With the goal of providing greater insight into the complex thermodynamics and kinetics ("thermokinetics") of mitochondrial energy transduction, a simple hydraulic analog model of oxidative phosphorylation is presented. In the hydraulic model, water tanks represent the forward and back "pressures" exerted by thermodynamic driving forces: the matrix redox potential (ΔGredox), the electrochemical potential for protons across the mitochondrial inner membrane (ΔGH), and the free energy of adenosine 5'-triphosphate (ATP) (ΔGATP). Net water flow proceeds from tanks with higher water pressure to tanks with lower pressure through "enzyme pipes" whose diameters represent the conductances (effective activities) of the proteins that catalyze the energy transfer. These enzyme pipes include the reactions of dehydrogenase enzymes, the electron transport chain (ETC), and the combined action of ATP synthase plus the ATP-adenosine 5'-diphosphate exchanger that spans the inner membrane. In addition, reactive oxygen species production is included in the model as a leak that is driven out of the ETC pipe by high pressure (high ΔGredox) and a proton leak dependent on the ΔGH for both its driving force and the conductance of the leak pathway. Model water pressures and flows are shown to simulate thermodynamic forces and metabolic fluxes that have been experimentally observed in mammalian skeletal muscle in response to acute exercise, chronic endurance training, and reduced substrate availability, as well as account for the thermokinetic behavior of mitochondria from fast- and slow-twitch skeletal muscle and the metabolic capacitance of the creatine kinase reaction.

Effect of Calcium on the Oxidative Phosphorylation Cascade in Skeletal Muscle Mitochondria

PubMed Central

Glancy, Brian; Willis, Wayne T; Chess, David J; Balaban, Robert S

2014-01-01

Calcium is believed to regulate mitochondrial oxidative phosphorylation, thereby contributing to the maintenance of cellular energy homeostasis. Skeletal muscle, with an energy conversion dynamic range of up to 100-fold, is an extreme case for evaluating the cellular balance of ATP production and consumption. This study examined the role of Ca2+ on the entire oxidative phosphorylation reaction network in isolated skeletal muscle mitochondria and attempted to extrapolate these results back to the muscle, in vivo. Kinetic analysis was conducted to evaluate the dose response effect of Ca2+ on the maximum velocity of oxidative phosphorylation (VmaxO) and the ADP affinity. Force-flow analysis evaluated the interplay between energetic driving forces and flux to determine the conductance, or effective activity, of individual steps within oxidative phosphorylation. Measured driving forces (extramitochondrial phosphorylation potential (ΔGATP), membrane potential, and redox states of NADH and cytochromes bH, bL, c1, c, and a,a3) were compared with flux (oxygen consumption) at 37°C. 840 nM Ca2+ generated a ∼2 fold increase in VmaxO with no change in ADP affinity (∼43 μM). Force-flow analysis revealed that Ca2+ activation of VmaxO was distributed throughout the oxidative phosphorylation reaction sequence. Specifically, Ca2+ increased the conductance of Complex IV (2.3-fold), Complexes I+III (2.2-fold), ATP production/transport (2.4-fold), and fuel transport/dehydrogenases (1.7-fold). These data support the notion that Ca2+ activates the entire muscle oxidative phosphorylation cascade, while extrapolation of these data to the exercising muscle predicts a significant role of Ca2+ in maintaining cellular energy homeostasis. PMID:23547908

Identification of general risk-management countermeasures for unsafe driving actions. Volume 3, A definitional study of speeding, following too closely, and driving left of center

DOT National Transportation Integrated Search

1981-02-01

The report develops a set of operational definitions for three unsafe driving actions (UDAs): speeding, following too closely, and driving left of center. The definitions flow from a methodological development and from an analysis of the literature a...

Turbulence, flow and transport: hints from reversed field pinch

NASA Astrophysics Data System (ADS)

Vianello, N.; Antoni, V.; Spada, E.; Spolaore, M.; Serianni, G.; Cavazzana, R.; Bergsåker, H.; Cecconello, M.; Drake, J. R.

2006-04-01

The interplay between sheared E × B flows and turbulence has been experimentally investigated in the edge region of the Extrap-T2R reversed field pinch experiment. Electrostatic fluctuations are found to rule the momentum balance equation representing the main driving term for sheared flows which counterbalances anomalous viscous damping. The driving role of electrostatic fluctuations is proved by the spatial structure of the Reynolds stress and by the time behaviour of the mean energy production term which supports the existence of an energy exchange from the small scales of turbulence to the larger scales of the mean flow.

Neuropsychological assessment of driving ability and self-evaluation: a comparison between driving offenders and a control group.

PubMed

Zingg, Christina; Puelschen, Dietrich; Soyka, Michael

2009-12-01

The relationship between performance in neuropsychological tests and actual driving performance is unclear and results of studies on this topic differ. This makes it difficult to use neuropsychological tests to assess driving ability. The ability to compensate cognitive deficits plays a crucial role in this context. We compared neuropsychological test results and self-evaluation ratings between three groups: driving offenders with a psychiatric diagnosis relevant for driving ability (mainly alcohol dependence), driving offenders without such a diagnosis and a control group of non-offending drivers. Subjects were divided into two age categories (19-39 and 40-66 years). It was assumed that drivers with a psychiatric diagnosis relevant for driving ability and younger driving offenders without a psychiatric diagnosis would be less able to adequately assess their own capabilities than the control group. The driving offenders with a psychiatric diagnosis showed poorer concentration, reactivity, cognitive flexibility and problem solving, and tended to overassess their abilities in intelligence and attentional functions, compared to the other two groups. Conversely, younger drivers rather underassessed their performance.

Sandia’s Current Energy Conversion module for the Flexible-Mesh Delft3D flow solver v. 1.0

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chartand, Chris; Jagers, Bert

The DOE has funded Sandia National Labs (SNL) to develop an open-source modeling tool to guide the design and layout of marine hydrokinetic (MHK) arrays to maximize power production while minimizing environmental effects. This modeling framework simulates flows through and around a MHK arrays while quantifying environmental responses. As an augmented version of the Dutch company, Deltares’s, environmental hydrodynamics code, Delft3D, SNL-Delft3D-CEC-FM includes a new module that simulates energy conversion (momentum withdrawal) by MHK current energy conversion devices with commensurate changes in the turbulent kinetic energy and its dissipation rate. SNL-Delft3D-CEC-FM modified the Delft3D flexible mesh flow solver, DFlowFM.

Twelve testable hypotheses on the geobiology of weathering.

PubMed

Brantley, S L; Megonigal, J P; Scatena, F N; Balogh-Brunstad, Z; Barnes, R T; Bruns, M A; Van Cappellen, P; Dontsova, K; Hartnett, H E; Hartshorn, A S; Heimsath, A; Herndon, E; Jin, L; Keller, C K; Leake, J R; McDowell, W H; Meinzer, F C; Mozdzer, T J; Petsch, S; Pett-Ridge, J; Pregitzer, K S; Raymond, P A; Riebe, C S; Shumaker, K; Sutton-Grier, A; Walter, R; Yoo, K

2011-03-01

Critical Zone (CZ) research investigates the chemical, physical, and biological processes that modulate the Earth's surface. Here, we advance 12 hypotheses that must be tested to improve our understanding of the CZ: (1) Solar-to-chemical conversion of energy by plants regulates flows of carbon, water, and nutrients through plant-microbe soil networks, thereby controlling the location and extent of biological weathering. (2) Biological stoichiometry drives changes in mineral stoichiometry and distribution through weathering. (3) On landscapes experiencing little erosion, biology drives weathering during initial succession, whereas weathering drives biology over the long term. (4) In eroding landscapes, weathering-front advance at depth is coupled to surface denudation via biotic processes. (5) Biology shapes the topography of the Critical Zone. (6) The impact of climate forcing on denudation rates in natural systems can be predicted from models incorporating biogeochemical reaction rates and geomorphological transport laws. (7) Rising global temperatures will increase carbon losses from the Critical Zone. (8) Rising atmospheric P(CO2) will increase rates and extents of mineral weathering in soils. (9) Riverine solute fluxes will respond to changes in climate primarily due to changes in water fluxes and secondarily through changes in biologically mediated weathering. (10) Land use change will impact Critical Zone processes and exports more than climate change. (11) In many severely altered settings, restoration of hydrological processes is possible in decades or less, whereas restoration of biodiversity and biogeochemical processes requires longer timescales. (12) Biogeochemical properties impart thresholds or tipping points beyond which rapid and irreversible losses of ecosystem health, function, and services can occur. © 2011 Blackwell Publishing Ltd.

Modeling Simple Driving Tasks with a One-Boundary Diffusion Model

PubMed Central

Ratcliff, Roger; Strayer, David

2014-01-01

A one-boundary diffusion model was applied to the data from two experiments in which subjects were performing a simple simulated driving task. In the first experiment, the same subjects were tested on two driving tasks using a PC-based driving simulator and the psychomotor vigilance test (PVT). The diffusion model fit the response time (RT) distributions for each task and individual subject well. Model parameters were found to correlate across tasks which suggests common component processes were being tapped in the three tasks. The model was also fit to a distracted driving experiment of Cooper and Strayer (2008). Results showed that distraction altered performance by affecting the rate of evidence accumulation (drift rate) and/or increasing the boundary settings. This provides an interpretation of cognitive distraction whereby conversing on a cell phone diverts attention from the normal accumulation of information in the driving environment. PMID:24297620

76 FR 2727 - Proposed Collection of Information

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-14

... attrition, as well as what information or education needs would increase the conversion ratio. An online... description of collection: To understand which factors are driving recruitment attrition, as well as what...

Understanding the rapidity of subsurface storm flow response from a fracture-oriented shallow vadose through a new perspective

NASA Astrophysics Data System (ADS)

Zhao, Peng; Zhao, Pei; Liang, Chuan; Li, Tianyang; Zhou, Baojia

2017-01-01

Velocity and celerity in hydrologic systems are controlled by different mechanisms. Efforts were made through joint sample collection and the use of hydrographs and tracers to understand the rapidity of the subsurface flow response to rainstorms on hourly time scales. Three deep subsurface flows during four natural rainstorm events were monitored. The results show that (1) deeper discharge was observed early in responding rainfall events and yielded a high hydrograph amplitude; (2) a ratio index, k, reflecting the dynamic change of the rainfall perturbation intensity in subsurface flow, might reveal inner causal relationships between the flow index and the tracer signal index. Most values of k were larger than 1 at the perturbation stage but approximated 1 at the no-perturbation stage; and (3) for statistical analysis of tracer signals in subsurface flows, the total standard deviation was 17.2, 11.9, 7.4 and 3.5 at perturbation stages and 4.4, 2.5, 1.1, and 0.95 at the non-perturbation stage for observed events. These events were 3-7 times higher in the former rather than the later, reflecting that the variation of tracer signals primarily occurred under rainfall perturbation. Thus, we affirmed that the dynamic features of rainfall have a key effect on rapid processes because, besides the gravity, mechanical waves originating from dynamic rainfall features are another driving factor for conversion between different types of rainfall mechanical energy. A conceptual model for pressure wave propagation was proposed, in which virtual subsurface flow processes in a heterogeneous vadose zone under rainfall are analogous to the water hammer phenomenon in complex conduit systems. Such an analogy can allow pressure in a shallow vadose to increase and decrease and directly influence the velocity and celerity of the flow reflecting a mechanism for rapid subsurface hydrologic response processes in the shallow vadose zone.

Giant frequency down-conversion of the dancing acoustic bubble

PubMed Central

Deymier, P. A.; Keswani, M.; Jenkins, N.; Tang, C.; Runge, K.

2016-01-01

We have demonstrated experimentally the existence of a giant frequency down-conversion of the translational oscillatory motion of individual submillimeter acoustic bubbles in water in the presence of a high frequency (500 kHz) ultrasonic standing wave. The frequency of the translational oscillations (~170 Hz) is more than three orders of magnitude smaller than that of the driving acoustic wave. We elucidate the mechanism of this very slow oscillation with an analytical model leading to an equation of translational motion of a bubble taking the form of Mathieu’s equation. This equation illuminates the origin of the giant down conversion in frequency as arising from an unstable equilibrium. We also show that bubbles that form chains along the direction of the acoustic standing wave due to radiation interaction forces exhibit also translation oscillations that form a spectral band. This band extends approximately from 130 Hz up to nearly 370 Hz, a frequency range that is still at least three orders of magnitude lower than the frequency of the driving acoustic wave. PMID:27857217

Giant frequency down-conversion of the dancing acoustic bubble

NASA Astrophysics Data System (ADS)

Deymier, P. A.; Keswani, M.; Jenkins, N.; Tang, C.; Runge, K.

2016-11-01

We have demonstrated experimentally the existence of a giant frequency down-conversion of the translational oscillatory motion of individual submillimeter acoustic bubbles in water in the presence of a high frequency (500 kHz) ultrasonic standing wave. The frequency of the translational oscillations (~170 Hz) is more than three orders of magnitude smaller than that of the driving acoustic wave. We elucidate the mechanism of this very slow oscillation with an analytical model leading to an equation of translational motion of a bubble taking the form of Mathieu’s equation. This equation illuminates the origin of the giant down conversion in frequency as arising from an unstable equilibrium. We also show that bubbles that form chains along the direction of the acoustic standing wave due to radiation interaction forces exhibit also translation oscillations that form a spectral band. This band extends approximately from 130 Hz up to nearly 370 Hz, a frequency range that is still at least three orders of magnitude lower than the frequency of the driving acoustic wave.

Design and analysis of a new high frequency double-servo direct drive rotary valve

NASA Astrophysics Data System (ADS)

Zhu, Muzhi; Zhao, Shengdun; Li, Jingxiang

2016-12-01

Researchers have investigated direct drive valve for many years to solve problems, such as fluid force imbalance and switching frequency. The structure of the rotary valve has received considerable research interest because of its favorable dynamic properties and simple structure. This paper studied the high frequency doubleservo direct drive rotary valve (DDRV), and proposed a novel structure and drive method satisfying high reversing frequency and adequate quantity of flow. Servo motors are integrated into the valve by the innovative structure, which is designed to equilibrate the unbalanced radial fluid force with the symmetric distributed oil ports. Aside from the fast reversing function of the valve, the DDRV presented high performance in linearity of the flow quantity and valve opening as a result of the fan-shaped flow ports. In addition, a computational fluid dynamics (CFD) method based on Fluent was conducted to verify the flux regulation effect of the height change of the adjustable boss.

Centromere strength provides the cell biological basis for meiotic drive and karyotype evolution in mice.

PubMed

Chmátal, Lukáš; Gabriel, Sofia I; Mitsainas, George P; Martínez-Vargas, Jessica; Ventura, Jacint; Searle, Jeremy B; Schultz, Richard M; Lampson, Michael A

2014-10-06

Mammalian karyotypes (number and structure of chromosomes) can vary dramatically over short evolutionary time frames. There are examples of massive karyotype conversion, from mostly telocentric (centromere terminal) to mostly metacentric (centromere internal), in 10(2)-10(5) years. These changes typically reflect rapid fixation of Robertsonian (Rb) fusions, a common chromosomal rearrangement that joins two telocentric chromosomes at their centromeres to create one metacentric. Fixation of Rb fusions can be explained by meiotic drive: biased chromosome segregation during female meiosis in violation of Mendel's first law. However, there is no mechanistic explanation of why fusions would preferentially segregate to the egg in some populations, leading to fixation and karyotype change, while other populations preferentially eliminate the fusions and maintain a telocentric karyotype. Here we show, using both laboratory models and wild mice, that differences in centromere strength predict the direction of drive. Stronger centromeres, manifested by increased kinetochore protein levels and altered interactions with spindle microtubules, are preferentially retained in the egg. We find that fusions preferentially segregate to the polar body in laboratory mouse strains when the fusion centromeres are weaker than those of telocentrics. Conversely, fusion centromeres are stronger relative to telocentrics in natural house mouse populations that have changed karyotype by accumulating metacentric fusions. Our findings suggest that natural variation in centromere strength explains how the direction of drive can switch between populations. They also provide a cell biological basis of centromere drive and karyotype evolution. Copyright © 2014 Elsevier Ltd. All rights reserved.

An observational study of driving distractions on urban roads in Spain.

PubMed

Prat, F; Planes, M; Gras, M E; Sullman, M J M

2015-01-01

The present research investigated the prevalence of driver engagement in secondary tasks and whether there were any differences by age and gender, as well as day of the week and time of the day. Two independent researchers observed 6578 drivers at nine randomly selected urban locations in Girona, Spain. Nearly 20% of the drivers observed were engaged in some type of secondary task, with the most common being: conversing with a passenger (11.1%), smoking (3.7%) and talking on a handheld mobile phone (1.3%). Surprisingly there were no differences by gender, but there were age-related differences with younger drivers being more frequently observed engaged in a number of different types of secondary tasks while driving (i.e. drinking, talking on a handheld mobile phone, and texting or keying numbers). Logistic regression showed that younger drivers, and to a lesser extent middle-age drivers, were significantly more likely to be observed engaged in a technological distraction than older drivers. Conversely, non-technological distractions were significantly predicted by day of the week, time of the day and location. A substantial number of the drivers observed in this study were putting themselves at an increased risk of becoming involved in a crash by engaging in non-driving related tasks at the same time as driving. Furthermore, the higher crash rate among young drivers may be partially accounted for by their more frequent engagement in some types of secondary tasks while driving. Copyright © 2014. Published by Elsevier Ltd.

Talking and texting among teenage drivers: a glass half empty or half full?

PubMed

O'Brien, Natalie P; Goodwin, Arthur H; Foss, Robert D

2010-12-01

Cell phone use and text messaging in particular are associated with an increased risk of motor vehicle crashes. However, the frequency with which teenagers use cell phones while driving is still largely unknown. The current study obtained self-reported cell phone use behaviors while driving, including text messaging, along with beliefs about these actions, for a sample of licensed teenage drivers. Questionnaires were mailed to a random sample of 1947 high-school-age teens in 2 large metropolitan areas in North Carolina. Questionnaires were completed and returned by 537 teens, of whom 320 had an intermediate or full driver's license. In total, 45 percent of teens reported using a cell phone in some capacity during their most recent trip. Fifteen percent reported that they only talked on a cell phone, 15 percent sent or read a text message only, and 15 percent both talked and texted. More generally, 12 percent of teens reported that they often talked on a cell phone while driving, 4 percent reported that they often initiated a text conversation while driving, 11 percent said that they often replied to texts, and 23 percent often read text messages. Teens reported using several strategies to reduce the risk associated with using a cell phone while driving. Among teens who had ever talked on a cell phone while driving, 47 percent said that they try to keep their conversations short because they are driving. Among teens who had ever texted while driving, approximately half said that they often wait until it feels safe to read and reply to text messages (58% and 47%, respectively). Most teens surveyed reported having talked or read or sent a text message using a cell phone while driving. Somewhat less than half engaged in one of these behaviors the last time they drove. However, many teens reported using strategies to reduce this risk and in certain instances, cell phone nonuse was the normative behavior. Better measurement of the extent and nature of phone use while driving is needed.

Direction of unsaturated flow in a homogeneous and isotropic hillslope

USGS Publications Warehouse

Lu, Ning; Kaya, Basak Sener; Godt, Jonathan W.

2011-01-01

The distribution of soil moisture in a homogeneous and isotropic hillslope is a transient, variably saturated physical process controlled by rainfall characteristics, hillslope geometry, and the hydrological properties of the hillslope materials. The major driving mechanisms for moisture movement are gravity and gradients in matric potential. The latter is solely controlled by gradients of moisture content. In a homogeneous and isotropic saturated hillslope, absent a gradient in moisture content and under the driving force of gravity with a constant pressure boundary at the slope surface, flow is always in the lateral downslope direction, under either transient or steady state conditions. However, under variably saturated conditions, both gravity and moisture content gradients drive fluid motion, leading to complex flow patterns. In general, the flow field near the ground surface is variably saturated and transient, and the direction of flow could be laterally downslope, laterally upslope, or vertically downward. Previous work has suggested that prevailing rainfall conditions are sufficient to completely control these flow regimes. This work, however, shows that under time-varying rainfall conditions, vertical, downslope, and upslope lateral flow can concurrently occur at different depths and locations within the hillslope. More importantly, we show that the state of wetting or drying in a hillslope defines the temporal and spatial regimes of flow and when and where laterally downslope and/or laterally upslope flow occurs.

Direction of unsaturated flow in a homogeneous and isotropic hillslope

USGS Publications Warehouse

Lu, N.; Kaya, B.S.; Godt, J.W.

2011-01-01

The distribution of soil moisture in a homogeneous and isotropic hillslope is a transient, variably saturated physical process controlled by rainfall characteristics, hillslope geometry, and the hydrological properties of the hillslope materials. The major driving mechanisms for moisture movement are gravity and gradients in matric potential. The latter is solely controlled by gradients of moisture content. In a homogeneous and isotropic saturated hillslope, absent a gradient in moisture content and under the driving force of gravity with a constant pressure boundary at the slope surface, flow is always in the lateral downslope direction, under either transient or steady state conditions. However, under variably saturated conditions, both gravity and moisture content gradients drive fluid motion, leading to complex flow patterns. In general, the flow field near the ground surface is variably saturated and transient, and the direction of flow could be laterally downslope, laterally upslope, or vertically downward. Previous work has suggested that prevailing rainfall conditions are sufficient to completely control these flow regimes. This work, however, shows that under time-varying rainfall conditions, vertical, downslope, and upslope lateral flow can concurrently occur at different depths and locations within the hillslope. More importantly, we show that the state of wetting or drying in a hillslope defines the temporal and spatial regimes of flow and when and where laterally downslope and/or laterally upslope flow occurs. Copyright 2011 by the American Geophysical Union.

Investigation of operating parameters on CO2 splitting by dielectric barrier discharge plasma

NASA Astrophysics Data System (ADS)

Pan, CHEN; Jun, SHEN; Tangchun, RAN; Tao, YANG; Yongxiang, YIN

2017-12-01

Experiments of CO2 splitting by dielectric barrier discharge (DBD) plasma were carried out, and the influence of CO2 flow rate, plasma power, discharge voltage, discharge frequency on CO2 conversion and process energy efficiency were investigated. It was shown that the absolute quantity of CO2 decomposed was only proportional to the amount of conductive electrons across the discharge gap, and the electron amount was proportional to the discharge power; the energy efficiency of CO2 conversion was almost a constant at a lower level, which was limited by CO2 inherent discharge character that determined a constant gap electric field strength. This was the main reason why CO2 conversion rate decreased as the CO2 flow rate increase and process energy efficiency was decreased a little as applied frequency increased. Therefore, one can improve the CO2 conversion by less feed flow rate or larger discharge power in DBD plasma, but the energy efficiency is difficult to improve.

Continuous production of lipase-catalyzed biodiesel in a packed-bed reactor: optimization and enzyme reuse study.

PubMed

Chen, Hsiao-Ching; Ju, Hen-Yi; Wu, Tsung-Ta; Liu, Yung-Chuan; Lee, Chih-Chen; Chang, Cheng; Chung, Yi-Lin; Shieh, Chwen-Jen

2011-01-01

An optimal continuous production of biodiesel by methanolysis of soybean oil in a packed-bed reactor was developed using immobilized lipase (Novozym 435) as a catalyst in a tert-butanol solvent system. Response surface methodology (RSM) and Box-Behnken design were employed to evaluate the effects of reaction temperature, flow rate, and substrate molar ratio on the molar conversion of biodiesel. The results showed that flow rate and temperature have significant effects on the percentage of molar conversion. On the basis of ridge max analysis, the optimum conditions were as follows: flow rate 0.1 mL/min, temperature 52.1°C, and substrate molar ratio 1 : 4. The predicted and experimental values of molar conversion were 83.31 ± 2.07% and 82.81 ± .98%, respectively. Furthermore, the continuous process over 30 days showed no appreciable decrease in the molar conversion. The paper demonstrates the applicability of using immobilized lipase and a packed-bed reactor for continuous biodiesel synthesis.

Turbine disk cavity aerodynamics and heat transfer

NASA Technical Reports Server (NTRS)

Johnson, B. V.; Daniels, W. A.

1992-01-01

Experiments were conducted to define the nature of the aerodynamics and heat transfer for the flow within the disk cavities and blade attachments of a large-scale model, simulating the Space Shuttle Main Engine (SSME) turbopump drive turbines. These experiments of the aerodynamic driving mechanisms explored the following: (1) flow between the main gas path and the disk cavities; (2) coolant flow injected into the disk cavities; (3) coolant density; (4) leakage flows through the seal between blades; and (5) the role that each of these various flows has in determining the adiabatic recovery temperature at all of the critical locations within the cavities. The model and the test apparatus provide close geometrical and aerodynamic simulation of all the two-stage cavity flow regions for the SSME High Pressure Fuel Turbopump and the ability to simulate the sources and sinks for each cavity flow.

Delft3D turbine turbulence module v. 1.0.0

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chartrand, Chris; Jagers, Bert

2016-08-25

The DOE has funded Sandia National Labs (SNL) to develop an open-source modeling tool to guide the design and layout of marine hydrokinetic (MHK) arrays to maximize power production while minimizing environmental effects. This modeling framework simulates flows through and around a MHK arrays while quantifying environmental responses. As an augmented version of the Dutch company, Deltares’s, environmental hydrodynamics code, Delft3D, Delft3D-CEC includes a new module that simulates energy conversion (momentum withdrawal) by MHK current energy conversion devices with commensurate changes in the turbulent kinetic energy and its dissipation rate. The Following is a description of Deltares’s open-source code Delft3Dmore » from which Delft3D-CEC is built upon. “Delft3D is a world leading 3D modeling suite to investigate hydrodynamics, sediment transport and morphology and water quality for fluvial, estuarine and coastal environments. As per 1 January 2011, the Delft3D flow (FLOW), morphology (MOR) and waves (WAVE) modules are available in open source. The software is used and has proven his capabilities on many places around the world, like the Netherlands, USA, Hong Kong, Singapore, Australia, Venice, etc. The software is continuously improved and developed with innovating advanced modelling techniques as consequence of the research work of our institute and to stay world leading. The FLOW module is the heart of Delft3D and is a multi-dimensional (2D or 3D) hydrodynamic (and transport) simulation programme which calculates non-steady flow and transport phenomena resulting from tidal and meteorological forcing on a curvilinear, boundary fitted grid or sperical coordinates. In 3D simulations, the vertical grid is defined following the so-called sigma coordinate approach or Z-layer approach. The MOR module computes sediment transport (both suspended and bed total load) and morphological changes for an arbitrary number of cohesive and non-cohesive fractions. Both currents and waves act as driving forces and a wide variety of transport formulae have been incorporated. For the suspended load this module connects to the 2D or 3D advection-diffusion solver of the FLOW module; density effects may be taken into account. An essential feature of the MOR module is the dynamic feedback with the FLOW and WAVE modules, which allow the flows and waves to adjust themselves to the local bathymetry and allows for simulations on any time scale from days (storm impact) to centuries (system dynamics). It can keep track of the bed composition to build up a stratigraphic record. The MOR module may be extended to include extensive features to simulate dredging and dumping scenarios. For over 30 years Deltares has been in the forefront of these types of combined morphological simulation techniques.”« less

Computer-Assisted English Learning System Based on Free Conversation by Topic

ERIC Educational Resources Information Center

Choi, Sung-Kwon; Kwon, Oh-Woog; Kim, Young-Kil

2017-01-01

This paper aims to describe a computer-assisted English learning system using chatbots and dialogue systems, which allow free conversation outside the topic without limiting the learner's flow of conversation. The evaluation was conducted by 20 experimenters. The performance of the system based on a free conversation by topic was measured by the…

Negative viscosity from negative compressibility and axial flow shear stiffness in a straight magnetic field

DOE PAGES

Li, J. C.; Diamond, P. H.

2017-03-23

Here, negative compressibility ITG turbulence in a linear plasma device (CSDX) can induce a negative viscosity increment. However, even with this negative increment, we show that the total axial viscosity remains positive definite, i.e. no intrinsic axial flow can be generated by pure ITG turbulence in a straight magnetic field. This differs from the case of electron drift wave (EDW) turbulence, where the total viscosity can turn negative, at least transiently. When the flow gradient is steepened by any drive mechanism, so that the parallel shear flow instability (PSFI) exceeds the ITG drive, the flow profile saturates at a level close to the value above which PSFI becomes dominant. This saturated flow gradient exceeds the PSFI linear threshold, and grows withmore » $$\

The vertical structure of the circulation and dynamics in Hudson Shelf Valley

USGS Publications Warehouse

Lentz, Steven J.; Butman, Bradford; Harris, Courtney K.

2014-01-01

Hudson Shelf Valley is a 20–30 m deep, 5–10 km wide v-shaped submarine valley that extends across the Middle Atlantic Bight continental shelf. The valley provides a conduit for cross-shelf exchange via along-valley currents of 0.5 m s−1 or more. Current profile, pressure, and density observations collected during the winter of 1999–2000 are used to examine the vertical structure and dynamics of the flow. Near-bottom along-valley currents having times scales of a few days are driven by cross-shelf pressure gradients setup by wind stresses, with eastward (westward) winds driving onshore (offshore) flow within the valley. The along-valley momentum balance in the bottom boundary layer is predominantly between the pressure gradient and bottom stress because the valley bathymetry limits current veering. Above the bottom boundary layer, the flow veers toward an along-shelf (cross-valley) orientation and a geostrophic balance with some contribution from the wind stress (surface Ekman layer). The vertical structure and strength of the along-valley current depends on the magnitude and direction of the wind stress. During offshore flows driven by westward winds, the near-bottom stratification within the valley increases resulting in a thinner bottom boundary layer and weaker offshore currents. Conversely, during onshore flows driven by eastward winds the near-bottom stratification decreases resulting in a thicker bottom boundary layer and stronger onshore currents. Consequently, for wind stress magnitudes exceeding 0.1 N m−2, onshore along-valley transport associated with eastward wind stress exceeds the offshore transport associated with westward wind stress of the same magnitude.

Development of a Mechatronic Syringe Pump to Control Fluid Flow in a Microfluidic Device Based on Polyimide Film

NASA Astrophysics Data System (ADS)

Sek Tee, Kian; Sharil Saripan, Muhammad; Yap, Hiung Yin; Fhong Soon, Chin

2017-08-01

With the advancement in microfluidic technology, fluid flow control for syringe pump is always essential. In this paper, a mechatronic syringe pump will be developed and customized to control the fluid flow in a poly-dimethylsiloxane (PDMS) microfluidic device based on a polyimide laminating film. The syringe pump is designed to drive fluid with flow rates of 100 and 1000 μl/min which intended to drive continuous fluid in a polyimide based microfluidic device. The electronic system consists of an Arduino microcontroller board and a uni-polar stepper motor. In the system, the uni-polar stepper motor was coupled to a linear slider attached to the plunger of a syringe pump. As the motor rotates, the plunger pumps the liquid out of the syringe. The accuracy of the fluid flow rate was determined by adjusting the number of micro-step/revolution to drive the stepper motor to infuse fluid into the microfluidic device. With the precise control of the electronic system, the syringe pump could accurately inject fluid volume at 100 and 1000 μl/min into a microfluidic device.

Self-report measures of distractibility as correlates of simulated driving performance.

PubMed

Kass, Steven J; Beede, Kristen E; Vodanovich, Stephen J

2010-05-01

The present study investigated the relationship between self-reported measures pertaining to attention difficulties and simulated driving performance while distracted. Thirty-six licensed drivers participated in a simulator driving task while engaged in a cell phone conversation. The participants completed questionnaires assessing their tendency toward boredom, cognitive failures, and behaviors associated with attention deficit and hyperactivity. Scores on these measures were significantly correlated with various driving outcomes (e.g., speed, lane maintenance, reaction time). Significant relationships were also found between one aspect of boredom proneness (i.e., inability to generate interest or concentrate) and self-reports of past driving behavior (moving violations). The current study may aid in the understanding of how individual differences in driver distractibility may contribute to unsafe driving behaviors and accident involvement. Additionally, such measures may assist in the identification of individuals at risk for committing driving errors due to being easily distracted. The benefits and limitations of conducting and interpreting simulation research are discussed. Copyright (c) 2009 Elsevier Ltd. All rights reserved.

Method for driving two-phase turbines with enhanced efficiency

NASA Technical Reports Server (NTRS)

Elliott, D. G. (Inventor)

1985-01-01

A method for driving a two phase turbine characterized by an output shaft having at least one stage including a bladed rotor connected in driving relation with the shaft is described. A two phase fluid is introduced into one stage at a known flow velocity and caused to pass through the rotor for imparing angular velocity thereto. The angular velocity of the rotor is maintained at a value such that the angular velocity of the tips of the blades of the rotor is a velocity equal to at least 50% of the velocity of the flow of the two phase fluid.

Experimental research of flow servo-valve

NASA Astrophysics Data System (ADS)

Takosoglu, Jakub

Positional control of pneumatic drives is particularly important in pneumatic systems. Some methods of positioning pneumatic cylinders for changeover and tracking control are known. Choking method is the most development-oriented and has the greatest potential. An optimal and effective method, particularly when applied to pneumatic drives, has been searched for a long time. Sophisticated control systems with algorithms utilizing artificial intelligence methods are designed therefor. In order to design the control algorithm, knowledge about real parameters of servo-valves used in control systems of electro-pneumatic servo-drives is required. The paper presents the experimental research of flow servo-valve.

NASA and energy

NASA Technical Reports Server (NTRS)

1974-01-01

NASA technology contributions to create energy sources include direct solar heating and cooling systems, wind generation of electricity, solar thermal energy turbine drives, solar cells, and techniques for locating, producing, and collecting organic materials for conversion into fuel.

Mobile phone use during driving: Effects on speed and effectiveness of driver compensatory behaviour.

PubMed

Choudhary, Pushpa; Velaga, Nagendra R

2017-09-01

This study analysed and modelled the effects of conversation and texting (each with two difficulty levels) on driving performance of Indian drivers in terms of their mean speed and accident avoiding abilities; and further explored the relationship between speed reduction strategy of the drivers and their corresponding accident frequency. 100 drivers of three different age groups (young, mid-age and old-age) participated in the simulator study. Two sudden events of Indian context: unexpected crossing of pedestrians and joining of parked vehicles from road side, were simulated for estimating the accident probabilities. Generalized linear mixed models approach was used for developing linear regression models for mean speed and binary logistic regression models for accident probability. The results of the models showed that the drivers significantly compensated the increased workload by reducing their mean speed by 2.62m/s and 5.29m/s in the presence of conversation and texting tasks respectively. The logistic models for accident probabilities showed that the accident probabilities increased by 3 and 4 times respectively when the drivers were conversing or texting on a phone during driving. Further, the relationship between the speed reduction patterns and their corresponding accident frequencies showed that all the drivers compensated differently; but, among all the drivers, only few drivers, who compensated by reducing the speed by 30% or more, were able to fully offset the increased accident risk associated with the phone use. Copyright © 2017 Elsevier Ltd. All rights reserved.

Calculations of Alfven Wave Driving Forces, Plasma Flow and Current Drive in Tokamak Plasmas

NASA Astrophysics Data System (ADS)

Elfimov, Artur; Galvao, Ricardo; Amarante-Segundo, Gesil; Nascimento, Ivan

2000-10-01

A general form of time-averaged poloidal ponderomotive forces induced by fast and kinetic Alfvin waves by direct numerical calculations and in geometric optics approximation are analyzed on the basis of the collisionless two fluid (ions and electrons) magneto-hydrodynamics equation. Analytical approximations are used to clarify the effect of Larmour radius on radio-frequency (RF) ponderomotive forces and on poloidal flows induced by them in tokamak plasmas.The RF ponderomotive force is expressed as a sum of a gradient part and of a wave momentum transfer force, which is proportional to wave dissipation. The gradient electromagnetic stress force is combined with fluid dynamic (Reynolds) stress force. It is shown that accounting only Reynolds stress term can overestimate the plasma flow and it is found that the finite ion Larmor radius effect play fundamental role in ponderomotive forces that can drive a poloidal flow, which is larger than a flow driven by a wave momentum transfer force. Finally, balancing the RF forces by the electron-ion friction and viscous force the current and plasma flows driven by ponderomotive forces are calculated for tokamak plasmas, using a kinetic code [Phys. Plasmas, v.6 (1999) p.2437]. Strongly sheared current and plasma flow waves is found.

Evaluation of Floodplain Modifications to Reduce the Effect of Floods Using a Two-Dimensional Hydrodynamic Model of the Flint River at Albany, Georgia

USGS Publications Warehouse

Musser, Jonathan W.

2008-01-01

Potential flow characteristics of future flooding along a 4.8-mile reach of the Flint River in Albany, Georgia, were simulated using recent digital-elevation-model data and the U.S. Geological Survey finite-element surface-water modeling system for two-dimensional flow in the horizontal plane (FESWMS-2DH). The model was run at four water-surface altitudes at the Flint River at Albany streamgage (02352500): 181.5-foot (ft) altitude with a flow of 61,100 cubic feet per second (ft3/s), 184.5-ft altitude with a flow of 75,400 ft3/s, 187.5-ft altitude with a flow of 91,700 ft3/s, and 192.5-ft altitude with a flow of 123,000 ft3/s. The model was run to measure changes in inundated areas and water-surface altitudes for eight scenarios of possible modifications to the 4.8-mile reach on the Flint River. The eight scenarios include removing a human-made peninsula located downstream from Oglethorpe Boulevard, increasing the opening under the Oakridge Drive bridge, adding culverts to the east Oakridge Drive bridge approach, adding culverts to the east and west Oakridge Drive bridge approaches, adding an overflow across the oxbow north of Oakridge Drive, making the overflow into a channel, removing the Oakridge Drive bridge, and adding a combination of an oxbow overflow and culverts on both Oakridge Drive bridge approaches. The modeled inundation and water-surface altitude changes were mapped for use in evaluating the river modifications. The most effective scenario at reducing inundated area was the combination scenario. At the 187.5-ft altitude, the inundated area decreased from 4.24 square miles to 4.00 square miles. The remove-peninsula scenario was the least effective with a reduction in inundated area of less than 0.01 square miles. In all scenarios, the inundated area reduction increased with water-surface altitude, peaking at the 187.5-ft altitude. The inundated area reduction then decreased at the gage altitude of 192.5 ft.

In-use catalyst surface area and its relation to HC conversion efficiency and FTP emissions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Donahue, K.S.; Sabourin, M.A.; Larson, R.E.

1986-01-01

Surface area data, steady-state hydrocarbon conversion efficiency data, and hydrocarbon emissions results have been determined for catalysts collected by the U.S. Environmental Protection Agency from properly maintained 1981 and 1982 model year vehicles. Catalysts covered in this study were limited to those with three-way-plus-oxidation monolith technologies. Catalyst surface areas were measured using the BET method, conversion efficiencies were measured on an exhaust gas generator, and emissions results were determined using the Urban Driving Schedule of the Federal Test Procedure. Results indicate that correlation of catalyst surface area data with hydrocarbon conversion efficiency data and hydrocarbon emissions results is significant formore » the sample studied.« less

Considerations when using variable frequency drive technology for pond aquculture

USDA-ARS?s Scientific Manuscript database

Some farmers have decided to use variable frequency drives (VFDs) to control pump speed and water flow rate to reduce operational cost and costs associated with repairs and maintenance. Mixed performance issues with VFDs and electric motors have been reported. Examples include frequent drive failure...

A Meta-Analysis of Global Urban Land Expansion

PubMed Central

Seto, Karen C.; Fragkias, Michail; Güneralp, Burak; Reilly, Michael K.

2011-01-01

The conversion of Earth's land surface to urban uses is one of the most irreversible human impacts on the global biosphere. It drives the loss of farmland, affects local climate, fragments habitats, and threatens biodiversity. Here we present a meta-analysis of 326 studies that have used remotely sensed images to map urban land conversion. We report a worldwide observed increase in urban land area of 58,000 km2 from 1970 to 2000. India, China, and Africa have experienced the highest rates of urban land expansion, and the largest change in total urban extent has occurred in North America. Across all regions and for all three decades, urban land expansion rates are higher than or equal to urban population growth rates, suggesting that urban growth is becoming more expansive than compact. Annual growth in GDP per capita drives approximately half of the observed urban land expansion in China but only moderately affects urban expansion in India and Africa, where urban land expansion is driven more by urban population growth. In high income countries, rates of urban land expansion are slower and increasingly related to GDP growth. However, in North America, population growth contributes more to urban expansion than it does in Europe. Much of the observed variation in urban expansion was not captured by either population, GDP, or other variables in the model. This suggests that contemporary urban expansion is related to a variety of factors difficult to observe comprehensively at the global level, including international capital flows, the informal economy, land use policy, and generalized transport costs. Using the results from the global model, we develop forecasts for new urban land cover using SRES Scenarios. Our results show that by 2030, global urban land cover will increase between 430,000 km2 and 12,568,000 km2, with an estimate of 1,527,000 km2 more likely. PMID:21876770

Kolmogorov Turbulence Defeated by Anderson Localization for a Bose-Einstein Condensate in a Sinai-Oscillator Trap

NASA Astrophysics Data System (ADS)

Ermann, Leonardo; Vergini, Eduardo; Shepelyansky, Dima L.

2017-08-01

We study the dynamics of a Bose-Einstein condensate in a Sinai-oscillator trap under a monochromatic driving force. Such a trap is formed by a harmonic potential and a repulsive disk located in the center vicinity corresponding to the first experiments of condensate formation by Ketterle and co-workers in 1995. We allow that the external driving allows us to model the regime of weak wave turbulence with the Kolmogorov energy flow from low to high energies. We show that in a certain regime of weak driving and weak nonlinearity such a turbulent energy flow is defeated by the Anderson localization that leads to localization of energy on low energy modes. This is in a drastic contrast to the random phase approximation leading to energy flow to high modes. A critical threshold is determined above which the turbulent flow to high energies becomes possible. We argue that this phenomenon can be studied with ultracold atoms in magneto-optical traps.

Kolmogorov Turbulence Defeated by Anderson Localization for a Bose-Einstein Condensate in a Sinai-Oscillator Trap.

PubMed

Ermann, Leonardo; Vergini, Eduardo; Shepelyansky, Dima L

2017-08-04

We study the dynamics of a Bose-Einstein condensate in a Sinai-oscillator trap under a monochromatic driving force. Such a trap is formed by a harmonic potential and a repulsive disk located in the center vicinity corresponding to the first experiments of condensate formation by Ketterle and co-workers in 1995. We allow that the external driving allows us to model the regime of weak wave turbulence with the Kolmogorov energy flow from low to high energies. We show that in a certain regime of weak driving and weak nonlinearity such a turbulent energy flow is defeated by the Anderson localization that leads to localization of energy on low energy modes. This is in a drastic contrast to the random phase approximation leading to energy flow to high modes. A critical threshold is determined above which the turbulent flow to high energies becomes possible. We argue that this phenomenon can be studied with ultracold atoms in magneto-optical traps.

Radiant energy absorption studies for laser propulsion. [gas dynamics

NASA Technical Reports Server (NTRS)

Caledonia, G. E.; Wu, P. K. S.; Pirri, A. N.

1975-01-01

A study of the energy absorption mechanisms and fluid dynamic considerations for efficient conversion of high power laser radiation into a high velocity flow is presented. The objectives of the study are: (1) to determine the most effective absorption mechanisms for converting laser radiation into translational energy, and (2) to examine the requirements for transfer of the absorbed energy into a steady flow which is stable to disturbances in the absorption zone. A review of inverse Bremsstrahlung, molecular and particulate absorption mechanisms is considered and the steady flow and stability considerations for conversion of the laser power to a high velocity flow in a nozzle configuration is calculated. A quasi-one-dimensional flow through a nozzle was formulated under the assumptions of perfect gas.

Simulation of Dynamo Action Generated by a Precession Driven Flow.

NASA Astrophysics Data System (ADS)

Giesecke, A.; Vogt, T.; Gundrum, T.; Stefani, F.

2017-12-01

Since many years precession is regarded as an alternative flow drivingmechanism that may account, e.g., for remarkable features of theancient lunar magnetic field [Dwyer 2011; Noir 2013; Weiss 2014] or asa complementary power source for the geodynamo [Malkus 1968; Vanyo1991]. Precessional forcing is also of great interest from theexperimental point of view because it represents a natural forcingmechanism that allows an efficient driving of conducting fluid flowson the laboratory scale without making use of propellers orpumps. Within the project DRESDYN (DREsden Sodium facility for DYNamoand thermohydraulic studies) a dynamo experiment is under developmentat Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in which a precessiondriven flow of liquid sodium with a magnetic Reynolds number of up toRm=700 will be used to drive dynamo action.Our present study addresses preparative numerical simulations and flowmeasurements at a small model experiment running with water. Theresulting flow pattern and amplitude provide the essential ingredientsfor kinematic dynamo models that are used to estimate whether theparticular flow is able to drive a dynamo. In the strongly non-linearregime the flow essentially consists of standing inertial waves (see Figure). Most remarkable feature is the occurrence of a resonant-like axisymmetricmode which emerges around a precession ratio of Ωp/Ωc = 0.1on top of the directly forced re-circulation flow. The combination ofthis axisymmetric mode and the forced m=1 Kelvin mode is indeedcapable of driving a dynamo at a critical magnetic Reynolds number ofRmc=430 which is well within the range achievable in theexperiment. However, the occurrence of the axisymmetric mode slightlydepends on the absolute rotation rate of the cylinder and futureexperiments are required to indicate whether it persists at theextremely large Re that will be obtained in the large scale sodiumexperiment.

E × B flow shear drive of the linear low- n modes of EHO in the QH-mode regime [ E × B flow shear drive of EHO in the QH-mode regime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, G. S.; Wan, B. N.; Wang, Y. F.

A new mechanism is identified for driving the edge harmonic oscillations (EHOs) in the quiescent H-mode (QH-mode) regime, where a strong E × B flow shear destabilizes low-n kink/peeling modes, separately from the previously found Kelvin-Helmholtz drive. We find that the differential advection of mode vorticity by sheared E × B flows modifies the two-dimensional pattern of mode electrostatic potential perpendicular to the magnetic field lines, which in turn causes a radial expansion of the mode structure, an increase of field line bending away from the mode rational surface, and a reduction of inertial stabilization. This enhances the kink drivemore » as the parallel wavenumber increases significantly away from the rational surface where the magnetic shear is also strong. A newly developed model reproduces the observations that at high E × B flow shear only a few low-n modes remain unstable, consistent with the EHO behavior, while at low E × B flow shear the unstable mode spectrum is significantly broadened, consistent with the low-n broadband electromagnetic turbulence behavior observed recently in the DIII-D tokamak. This destabilization is also shown to be independent of the sign of the flow shear, as observed experimentally, and has not been taken into 2 / 46 account in previous pedestal linear stability analyses. Verification of the veracity of this EHO mechanism will require analysis of the nonlinear evolution of low-n kink/peeling modes so destabilized in the linear regime.« less

E × B flow shear drive of the linear low- n modes of EHO in the QH-mode regime [ E × B flow shear drive of EHO in the QH-mode regime

DOE PAGES

Xu, G. S.; Wan, B. N.; Wang, Y. F.; ...

2017-07-18

A new mechanism is identified for driving the edge harmonic oscillations (EHOs) in the quiescent H-mode (QH-mode) regime, where a strong E × B flow shear destabilizes low-n kink/peeling modes, separately from the previously found Kelvin-Helmholtz drive. We find that the differential advection of mode vorticity by sheared E × B flows modifies the two-dimensional pattern of mode electrostatic potential perpendicular to the magnetic field lines, which in turn causes a radial expansion of the mode structure, an increase of field line bending away from the mode rational surface, and a reduction of inertial stabilization. This enhances the kink drivemore » as the parallel wavenumber increases significantly away from the rational surface where the magnetic shear is also strong. A newly developed model reproduces the observations that at high E × B flow shear only a few low-n modes remain unstable, consistent with the EHO behavior, while at low E × B flow shear the unstable mode spectrum is significantly broadened, consistent with the low-n broadband electromagnetic turbulence behavior observed recently in the DIII-D tokamak. This destabilization is also shown to be independent of the sign of the flow shear, as observed experimentally, and has not been taken into 2 / 46 account in previous pedestal linear stability analyses. Verification of the veracity of this EHO mechanism will require analysis of the nonlinear evolution of low-n kink/peeling modes so destabilized in the linear regime.« less

Driving Chemical Reactions in Plasmonic Nanogaps with Electrohydrodynamic Flow.

PubMed

Thrift, William J; Nguyen, Cuong Q; Darvishzadeh-Varcheie, Mahsa; Zare, Siavash; Sharac, Nicholas; Sanderson, Robert N; Dupper, Torin J; Hochbaum, Allon I; Capolino, Filippo; Abdolhosseini Qomi, Mohammad Javad; Ragan, Regina

2017-11-28

Nanoparticles from colloidal solution-with controlled composition, size, and shape-serve as excellent building blocks for plasmonic devices and metasurfaces. However, understanding hierarchical driving forces affecting the geometry of oligomers and interparticle gap spacings is still needed to fabricate high-density architectures over large areas. Here, electrohydrodynamic (EHD) flow is used as a long-range driving force to enable carbodiimide cross-linking between nanospheres and produces oligomers exhibiting sub-nanometer gap spacing over mm 2 areas. Anhydride linkers between nanospheres are observed via surface-enhanced Raman scattering (SERS) spectroscopy. The anhydride linkers are cleavable via nucleophilic substitution and enable placement of nucleophilic molecules in electromagnetic hotspots. Atomistic simulations elucidate that the transient attractive force provided by EHD flow is needed to provide a sufficient residence time for anhydride cross-linking to overcome slow reaction kinetics. This synergistic analysis shows assembly involves an interplay between long-range driving forces increasing nanoparticle-nanoparticle interactions and probability that ligands are in proximity to overcome activation energy barriers associated with short-range chemical reactions. Absorption spectroscopy and electromagnetic full-wave simulations show that variations in nanogap spacing have a greater influence on optical response than variations in close-packed oligomer geometry. The EHD flow-anhydride cross-linking assembly method enables close-packed oligomers with uniform gap spacings that produce uniform SERS enhancement factors. These results demonstrate the efficacy of colloidal driving forces to selectively enable chemical reactions leading to future assembly platforms for large-area nanodevices.

Chapter 13: Water and Forests

Treesearch

Graeme Lockaby; Chelsea Nagy; James M. Vose; Chelcy R. Ford; Ge Sun; Steve McNulty; Pete Caldwell; Erika Cohen; Jennifer Moore Meyers

2011-01-01

Forest conversion to agriculture or urban use consistently causes increased discharge, peak flow, and velocity of streams. Subregional differences in hydrologic responses to urbanization are substantial. Sediment, water chemistry indices, pathogens, and other substances often become more concentrated after forest conversion. If the conversion is to an urban use, the...

Left and right ventricular hemodynamic forces in healthy volunteers and elite athletes assessed with 4D flow magnetic resonance imaging.

PubMed

Arvidsson, Per M; Töger, Johannes; Carlsson, Marcus; Steding-Ehrenborg, Katarina; Pedrizzetti, Gianni; Heiberg, Einar; Arheden, Håkan

2017-02-01

Intracardiac blood flow is driven by hemodynamic forces that are exchanged between the blood and myocardium. Previous studies have been limited to 2D measurements or investigated only left ventricular (LV) forces. Right ventricular (RV) forces and their mechanistic contribution to asymmetric redirection of flow in the RV have not been measured. We therefore aimed to quantify 3D hemodynamic forces in both ventricles in a cohort of healthy subjects, using magnetic resonance imaging 4D flow measurements. Twenty five controls, 14 elite endurance athletes, and 2 patients with LV dyssynchrony were included. 4D flow data were used as input for the Navier-Stokes equations to compute hemodynamic forces over the entire cardiac cycle. Hemodynamic forces were found in a qualitatively consistent pattern in all healthy subjects, with variations in amplitude. LV forces were mainly aligned along the apical-basal longitudinal axis, with an additional component aimed toward the aortic valve during systole. Conversely, RV forces were found in both longitudinal and short-axis planes, with a systolic force component driving a slingshot-like acceleration that explains the mechanism behind the redirection of blood flow toward the pulmonary valve. No differences were found between controls and athletes when indexing forces to ventricular volumes, indicating that cardiac force expenditures are tuned to accelerate blood similarly in small and large hearts. Patients' forces differed from controls in both timing and amplitude. Normal cardiac pumping is associated with specific force patterns for both ventricles, and deviation from these forces may be a sensitive marker of ventricular dysfunction. Reference values are provided for future studies. NEW & NOTEWORTHY Biventricular hemodynamic forces were quantified for the first time in healthy controls and elite athletes (n = 39). Hemodynamic forces constitute a slingshot-like mechanism in the right ventricle, redirecting blood flow toward the pulmonary circulation. Force patterns were similar between healthy subjects and athletes, indicating potential utility as a cardiac function biomarker. Copyright © 2017 the American Physiological Society.

Particle migration and sorting in microbubble streaming flows

PubMed Central

Thameem, Raqeeb; Hilgenfeldt, Sascha

2016-01-01

Ultrasonic driving of semicylindrical microbubbles generates strong streaming flows that are robust over a wide range of driving frequencies. We show that in microchannels, these streaming flow patterns can be combined with Poiseuille flows to achieve two distinctive, highly tunable methods for size-sensitive sorting and trapping of particles much smaller than the bubble itself. This method allows higher throughput than typical passive sorting techniques, since it does not require the inclusion of device features on the order of the particle size. We propose a simple mechanism, based on channel and flow geometry, which reliably describes and predicts the sorting behavior observed in experiment. It is also shown that an asymptotic theory that incorporates the device geometry and superimposed channel flow accurately models key flow features such as peak speeds and particle trajectories, provided it is appropriately modified to account for 3D effects caused by the axial confinement of the bubble. PMID:26958103

Aqueous Lithium-Iodine Solar Flow Battery for the Simultaneous Conversion and Storage of Solar Energy.

PubMed

Yu, Mingzhe; McCulloch, William D; Beauchamp, Damian R; Huang, Zhongjie; Ren, Xiaodi; Wu, Yiying

2015-07-08

Integrating both photoelectric-conversion and energy-storage functions into one device allows for the more efficient solar energy usage. Here we demonstrate the concept of an aqueous lithium-iodine (Li-I) solar flow battery (SFB) by incorporation of a built-in dye-sensitized TiO2 photoelectrode in a Li-I redox flow battery via linkage of an I3(-)/I(-) based catholyte, for the simultaneous conversion and storage of solar energy. During the photoassisted charging process, I(-) ions are photoelectrochemically oxidized to I3(-), harvesting solar energy and storing it as chemical energy. The Li-I SFB can be charged at a voltage of 2.90 V under 1 sun AM 1.5 illumination, which is lower than its discharging voltage of 3.30 V. The charging voltage reduction translates to energy savings of close to 20% compared to conventional Li-I batteries. This concept also serves as a guiding design that can be extended to other metal-redox flow battery systems.

Monitoring the Thickness of Coal-Conversion Slag

NASA Technical Reports Server (NTRS)

Walsh, J. V.

1984-01-01

Technique adapts analogous ocean-floor-mapping technology. Existing ocean floor acoustic technology adapted for real-time monitoring of thickness and viscosity of flowing slag in coal-conversion processing.

Analysis of mixed traffic flow with human-driving and autonomous cars based on car-following model

NASA Astrophysics Data System (ADS)

Zhu, Wen-Xing; Zhang, H. M.

2018-04-01

We investigated the mixed traffic flow with human-driving and autonomous cars. A new mathematical model with adjustable sensitivity and smooth factor was proposed to describe the autonomous car's moving behavior in which smooth factor is used to balance the front and back headway in a flow. A lemma and a theorem were proved to support the stability criteria in traffic flow. A series of simulations were carried out to analyze the mixed traffic flow. The fundamental diagrams were obtained from the numerical simulation results. The varying sensitivity and smooth factor of autonomous cars affect traffic flux, which exhibits opposite varying tendency with increasing parameters before and after the critical density. Moreover, the sensitivity of sensors and smooth factors play an important role in stabilizing the mixed traffic flow and suppressing the traffic jam.

Liquid-metal flows: Magnetohydrodynamics and applications; Proceedings of the Fifth Beersheba International Seminar on Magnetohydrodynamic Flows and Turbulence, University of the Negev, Beersheba, Israel, Mar. 2-6, 1987

DOE Office of Scientific and Technical Information (OSTI.GOV)

Branover, H.; Mond, M.; Unger, Y.

The present collection of papers on MHD-related uses of liquid metal flows and their applications discusses topics in laminar MHD flows, MHD power generation, metallurgical MHD applications, and two-phase MHD flows. Attention is given to MHD flows with closed streamlines, nonlinear waves in liquid metals under a transverse magnetic field, liquid-metal MHD conversion of nuclear energy to electricity, the testing of optimized MHD conversion (OMACON) systems, and aspects of a liquid-metal induction generator. Also discussed are MHD effects in liquid-metal breeder reactors, a plasma-driven MHD powerplant, modeling the recirculating flows in channel-induction surfaces, the hydrodynamics of aluminum reduction cells, free-surfacemore » determination in a levitation-melting process, the parametric interactions of waves in bubbly liquid metals, and the occurrence of cavitation in water jets.« less

Complex Flow: Workshop Report; January 17-18, 2012, University of Colorado, Boulder

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

2012-06-01

The Department of Energy's Wind Program organized a two-day workshop designed to examine complex wind flow into and out of the wind farm environment and the resulting impacts on the mechanical workings of individual wind turbines. An improved understanding of these processes will subsequently drive down the risk involved for wind energy developers, financiers, and owner/operators, thus driving down the cost of energy.

Energy configuration optimization of submerged propeller in oxidation ditch based on CFD

NASA Astrophysics Data System (ADS)

Wu, S. Y.; Zhou, D. Q.; Zheng, Y.

2012-11-01

The submerged propeller is presented as an important dynamic source in oxidation ditch. In order to guarantee the activated sludge not deposit, it is necessary to own adequate drive power. Otherwise, it will cause many problems such as the awful mixed flow and the great consuming of energy. At present, carrying on the installation optimization of submerged propeller in oxidation ditch mostly depends on experience. So it is necessary to use modern design method to optimize the installation position and number of submerged propeller, and to research submerged propeller flow field characteristics. The submerged propeller internal flow is simulated by using CFD software FLUENT6.3. Based on Navier-Stokes equations and standard k - ɛ turbulence model, the flow was simulated by using a SIMPLE algorithm. The results indicate that the submerged propeller installation position change could avoid the condition of back mixing, which caused by the strong drive. Besides, the problem of sludge deposit and the low velocity in the bend which caused by the drive power attenuation could be solved. By adjusting the submerged propeller number, the least power density that the mixing drive needed could be determined and saving energy purpose could be achieved. The study can provide theoretical guidance for optimize the submerged propeller installation position and determine submerged propeller number.

Protein folding: complex potential for the driving force in a two-dimensional space of collective variables.

PubMed

Chekmarev, Sergei F

2013-10-14

Using the Helmholtz decomposition of the vector field of folding fluxes in a two-dimensional space of collective variables, a potential of the driving force for protein folding is introduced. The potential has two components. One component is responsible for the source and sink of the folding flows, which represent respectively, the unfolded states and the native state of the protein, and the other, which accounts for the flow vorticity inherently generated at the periphery of the flow field, is responsible for the canalization of the flow between the source and sink. The theoretical consideration is illustrated by calculations for a model β-hairpin protein.

Flow Cells for Scalable Energy Conversion and Storage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukundan, Rangachary

2017-10-26

This project is a response to current flow systems that are V-aqueous and not cost effective. It will hopefully enable high energy/ power density flow cells through rational materials and system design.

CO2 laser drives extreme ultraviolet nano-lithography — second life of mature laser technology

NASA Astrophysics Data System (ADS)

Nowak, K. M.; Ohta, T.; Suganuma, T.; Fujimoto, J.; Mizoguchi, H.; Sumitani, A.; Endo, A.

2013-12-01

It was shown both theoretically and experimentally that nanosecond order laser pulses at 10.6 micron wavelength were superior for driving the Sn plasma extreme ultraviolet (EUV) source for nano-lithography for the reasons of higher conversion efficiency, lower production of debris and higher average power levels obtainable in CO2 media without serious problems of beam distortions and nonlinear effects occurring in competing solid-state lasers at high intensities. The renewed interest in such pulse format, wavelength, repetition rates in excess of 50 kHz and average power levels in excess of 18 kiloWatt has sparked new opportunities for a matured multi-kiloWatt CO2 laser technology. The power demand of EUV source could be only satisfied by a Master-Oscillator-Power-Amplifier system configuration, leading to a development of a new type of hybrid pulsed CO2 laser employing a whole spectrum of CO2 technology, such as fast flow systems and diffusion-cooled planar waveguide lasers, and relatively recent quantum cascade lasers. In this paper we review briefly the history of relevant pulsed CO2 laser technology and the requirements for multi-kiloWatt CO2 laser, intended for the laser-produced plasma EUV source, and present our recent advances, such as novel solid-state seeded master oscillator and efficient multi-pass amplifiers built on planar waveguide CO2 lasers.

Thermodynamic modelling and solar reactor design for syngas production through SCWG of algae

NASA Astrophysics Data System (ADS)

Venkataraman, Mahesh B.; Rahbari, Alireza; Pye, John

2017-06-01

Conversion of algal biomass into value added products, such as liquid fuels, using solar-assisted supercritical water gasification (SCWG) offers a promising approach for clean fuel production. SCWG has significant advantages over conventional gasification in terms of flexibility of feedstock, faster intrinsic kinetics and lower char formation. A relatively unexplored avenue in SCWG is the use of non-renewable source of energy for driving the endothermic gasification. The use of concentrated solar thermal to provide the process heat is attractive, especially in the case of expensive feedstocks such as algae. This study attempts to identify the key parameters and constraints in designing a solar cavity receiver/reactor for on-sun SCWG of algal biomass. A tubular plug-flow reactor, operating at 24 MPa and 400-600 °C with a solar input of 20MWth is modelled. Solar energy is utilized to increase the temperature of the reaction medium (10 wt.% algae solution) from 400 to 605 °C and simultaneously drive the gasification. The model additionally incorporates material constraints based on the allowable stresses for a commercially available Ni-based alloy (Inconel 625), and exergy accounting for the cavity reactor. A parametric evaluation of the steady state performance and quantification of the losses through wall conduction, external radiation and convection, internal convection, frictional pressure drop, mixing and chemical irreversibility, is presented.

Fully alternating, triaxial electric or magnetic fields offer new routes to fluid vorticity

DOE PAGES

Martin, James E.; Solis, Kyle J.

2014-10-31

Noncontact methods of generating strong fluid vorticity are important to problems involving heat and mass transfer, fluid mixing, active wetting, and droplet transport. Furthermore, because zero or even negative shear viscosities can be induced, vorticity can greatly extend the control range of the smart fluids used in magnetorheological devices. In recent work we have shown that a particular class of ac/ac/dc triaxial fields (so-called symmetry-breaking rational fields) can create strong vorticity in magnetic particle suspensions and have presented a theory of the vorticity that is based on the symmetry of the 2-d Lissajous trajectories of the field and its converse.more » In this paper we demonstrate that there are three countably infinite sets of fully alternating ac/ac/ac triaxial fields whose frequencies form rational triads that have the symmetry required to drive fluid vorticity. The symmetry of the 3-d Lissajous trajectories of the field and its converse can be derived and from this the direction of the vorticity axis can be predicted, as can the dependence of the sign of the vorticity on the phase relations between the three field components. Experimental results are presented that validate the symmetry theory. These discoveries significantly broaden the class of triaxial fields that can be exploited to produce strong noncontact flow.« less

The dangers of rumination on the road: Predictors of risky driving.

PubMed

Suhr, Kyle A; Dula, Chris S

2017-02-01

Past studies found many different types of factors can influence dangerous driving behaviors. Driver inattention, such as driving under the influence or using a cell phone while driving, was found to contribute to risky driving behaviors. Rumination is a cognitive process that may also contribute to risky driving behaviors due to its influence on attention and limited executive processes. The present study explores the potential role of rumination in dangerous driving behavior endorsement. It was hypothesized that trait rumination would be significantly related to dangerous driving behaviors and that this relationship would be conditional to the sex of the participant. Six-hundred and fifty-three Southeastern university students were recruited to participate and asked to complete multiple questionnaires measuring anger rumination, thought content, driving anger, and dangerous driving behaviors. It was demonstrated that self-reported risky driving behaviors significantly predicted dangerous driving behavior endorsement on the Dula Dangerous Driving Index. Trait rumination scores were found to predict self-reported dangerous driving, aggressive driving, and risky driving behaviors as well as trait driving anger scores. However, no conditional effects based on the sex of the participant were found. It appeared males and females were equally likely to report dangerous driving behaviors, driving anger thoughts, and trait anger rumination. Findings from the current study may assist in understanding how cognitive processes influence different driving behaviors and help develop methods to re-direct attention to safe driving behaviors, and conversely away from ruminative thoughts that increase the likelihood of dangerous driving. Copyright © 2016 Elsevier Ltd. All rights reserved.

Electron transfer in biology

NASA Astrophysics Data System (ADS)

Williams, R. J. P.

Electron transfer is one of the key reactions of biology not just in catalysis of oxidation/reduction reactions but in the conversion of sources of energy such as light to usable form for chemical transformations. There are then two intriguing problems. What is the nature of the matrix in which electrons flow in a biological cell after the initial charge separation due for example to the absorption of light. Here we are examining biological structures similar to man's electronic wires and the construction must be of low resistance in what are apparently insulators - organic polymers. It has been found that the electronic conduction system is largely made from metallo-proteins associated with lipid membranes. We understand much about these biological wires today. The second problem concerns the conversion of the energy captured from the light into usable chemical form. The major synthetic step in the production of biological polymers, including proteins, DNA, RNA, polysaccharides and fats, is condensation, i.e. the removal of water in the formation of amides, esters and so on. Now these condensation reactions are driven in biology by using a drying agent in water, namely the anhydride, pyrophosphate, in a special compound ATP, adenosine triphosphate. The central problem is to discover exactly how the flow of electrons can be related to the synthesis of (bound) pyrophosphate. (In a thermodynamic sense pyrophosphate is a water soluble kinetically stable drying agent comparable with solid P2O5.) In the biological systems the connection between these different classes of reaction, electron transfer and condensation, is known to be via the production of an energized gradient of protons across the biological membrane which arises from the flow of electrons across the same membrane in the electron transport wires of biology. However we do not understand thoroughly the steps which lead from electron flow in a membrane to proton gradients in that membrane, i.e. electron/proton coupling. Again we do not understand thoroughly how subsequently the proton gradient across a membrane makes ATP, pyrophosphate. Today there is good experimental evidence as to the likely answers in principle. These analyse the coupling devices in mechanical terms. In this article I describe at first the 'wires' of biology, uncoupled simple electron flow, and then go on to the ways in which electron flow could be transduced by mechanical devices, also proteins, into proton gradients and then ATP. This will be termed coupled electron flow. The objective of the article is to stimulate participation by physical chemists in the further description of biological energy capture from light or the oxidation of hydrocarbons to a form suitable for driving chemical syntheses in a controlled manner.

Modeling mechanical restriction differences between car and heavy truck in two-lane cellular automata traffic flow model

NASA Astrophysics Data System (ADS)

Li, Xin; Li, Xingang; Xiao, Yao; Jia, Bin

2016-06-01

Real traffic is heterogeneous with car and truck. Due to mechanical restrictions, the car and the truck have different limited deceleration capabilities, which are important factors in safety driving. This paper extends the single lane safety driving (SD) model with limited deceleration capability to two-lane SD model, in which car-truck heterogeneous traffic is considered. A car has a larger limited deceleration capability while a heavy truck has a smaller limited deceleration capability as a result of loaded goods. Then the safety driving conditions are different as the types of the following and the leading vehicles vary. In order to eliminate the well-known plug in heterogeneous two-lane traffic, it is assumed that heavy truck has active deceleration behavior when the heavy truck perceives the forming plug. The lane-changing decisions are also determined by the safety driving conditions. The fundamental diagram, spatiotemporal diagram, and lane-changing frequency were investigated to show the effect of mechanical restriction on heterogeneous traffic flow. It was shown that there would be still three traffic phases in heterogeneous traffic condition; the active deceleration of the heavy truck could well eliminate the plug; the lane-changing frequency was low in synchronized flow; the flow and velocity would decrease as the proportion of heavy truck grows or the limited deceleration capability of heavy truck drops; and the flow could be improved with lane control measures.

Distracted Driving in Teens with and without ADHD

DOT National Transportation Integrated Search

2010-01-01

To determine the effect cell phone conversation or text messaging has on motor : vehicle collision-related injury risk in teens with or without Attention Deficit/Hyperactivity : Disorder Combined Type (ADHD-C) and whether a computerized cognitive...

The potential for mode conversion to rail service in Wisconsin.

DOT National Transportation Integrated Search

2016-07-01

The team built upon the Wisconsin Economic Development Corporations study regarding industries that drive the Wisconsin economy, : and complemented the efforts of the Wisconsin Central Group and Wisconsin Manufacturers Commerce by geo-locating shi...

Development of a J-T Micro Compressor

NASA Astrophysics Data System (ADS)

Champagne, P.; Olson, J. R.; Nast, T.; Roth, E.; Collaco, A.; Kaldas, G.; Saito, E.; Loung, V.

2015-12-01

Lockheed Martin has developed and tested a space-quality compressor capable of delivering closed-loop gas flow with a high pressure ratio, suitable for driving a Joule- Thomson cold head. The compressor is based on a traditional “Oxford style” dual-opposed piston compressor with linear drive motors and flexure-bearing clearance-seal technology for high reliability and long life. This J-T compressor retains the approximate size, weight, and cost of the ultra-compact, 200 gram Lockheed Martin Pulse Tube Micro Compressor, despite the addition of a flow-rectifying system to convert the AC pressure wave into a steady flow.

Pleistocene glacial cycles drive isolation, gene flow and speciation in the high-elevation Andes.

PubMed

Nevado, Bruno; Contreras-Ortiz, Natalia; Hughes, Colin; Filatov, Dmitry A

2018-06-04

Mountain ranges are amongst the most species-rich habitats, with many large and rapid evolutionary radiations. The tempo and mode of diversification in these systems are key unanswered questions in evolutionary biology. Here we study the Andean Lupinus radiation to understand the processes driving very rapid diversification in montane systems. We use genomic and transcriptomic data of multiple species and populations, and apply phylogenomic and demographic analyses to test whether diversification proceeded without interspecific gene flow - as expected if Andean orogeny and geographic isolation were the main drivers of diversification - or if diversification was accompanied by gene flow, in which case other processes were probably involved. We uncover several episodes of gene flow between species, including very recent events likely to have been prompted by changes in habitat connectivity during Pleistocene glacial cycles. Furthermore, we find that gene flow between species was heterogeneously distributed across the genome. We argue that exceptionally fast diversification of Andean Lupinus was partly a result of Late Pleistocene glacial cycles, with associated cycles of expansion and contraction driving geographic isolation or secondary contact of species. Furthermore, heterogeneous gene flow across the genome suggests a role for selection and ecological speciation in rapid diversification in this system. © 2018 The Authors New Phytologist © 2018 New Phytologist Trust.

Liquid Acquisition Device Design Sensitivity Study

NASA Technical Reports Server (NTRS)

VanDyke, M. K.; Hastings, L. J.

2012-01-01

In-space propulsion often necessitates the use of a capillary liquid acquisition device (LAD) to assure that gas-free liquid propellant is available to support engine restarts in microgravity. If a capillary screen-channel device is chosen, then the designer must determine the appropriate combination screen mesh and channel geometry. A screen mesh selection which results in the smallest LAD width when compared to any other screen candidate (for a constant length) is desirable; however, no best screen exists for all LAD design requirements. Flow rate, percent fill, and acceleration are the most influential drivers for determining screen widths. Increased flow rates and reduced percent fills increase the through-the-screen flow pressure losses, which drive the LAD to increased widths regardless of screen choice. Similarly, increased acceleration levels and corresponding liquid head pressures drive the screen mesh selection toward a higher bubble point (liquid retention capability). After ruling out some screens on the basis of acceleration requirements alone, candidates can be identified by examining screens with small flow-loss-to-bubble point ratios for a given condition (i.e., comparing screens at certain flow rates and fill levels). Within the same flow rate and fill level, the screen constants inertia resistance coefficient, void fraction, screen pore or opening diameter, and bubble point can become the driving forces in identifying the smaller flow-loss-to-bubble point ratios.

Designing interfaces of hydrogenase-nanomaterial hybrids for efficient solar conversion.

PubMed

King, Paul W

2013-01-01

The direct conversion of sunlight into biofuels is an intriguing alternative to a continued reliance on fossil fuels. Natural photosynthesis has long been investigated both as a potential solution, and as a model for utilizing solar energy to drive a water-to-fuel cycle. The molecules and organizational structure provide a template to inspire the design of efficient molecular systems for photocatalysis. A clear design strategy is the coordination of molecular interactions that match kinetic rates and energetic levels to control the direction and flow of energy from light harvesting to catalysis. Energy transduction and electron-transfer reactions occur through interfaces formed between complexes of donor-acceptor molecules. Although the structures of several of the key biological complexes have been solved, detailed descriptions of many electron-transfer complexes are lacking, which presents a challenge to designing and engineering biomolecular systems for solar conversion. Alternatively, it is possible to couple the catalytic power of biological enzymes to light harvesting by semiconductor nanomaterials. In these molecules, surface chemistry and structure can be designed using ligands. The passivation effect of the ligand can also dramatically affect the photophysical properties of the semiconductor, and energetics of external charge-transfer. The length, degree of bond saturation (aromaticity), and solvent exposed functional groups of ligands can be manipulated to further tune the interface to control molecular assembly, and complex stability in photocatalytic hybrids. The results of this research show how ligand selection is critical to designing molecular interfaces that promote efficient self-assembly, charge-transfer and photocatalysis. This article is part of a Special Issue entitled: Metals in Bioenergetics and Biomimetics Systems. Copyright © 2013 Elsevier B.V. All rights reserved.

CO2 conversion in non-thermal plasma and plasma/g-C3N4 catalyst hybrid processes

NASA Astrophysics Data System (ADS)

Lu, Na; Sun, Danfeng; Zhang, Chuke; Jiang, Nan; Shang, Kefeng; Bao, Xiaoding; Li, Jie; Wu, Yan

2018-03-01

Carbon dioxide conversion at atmosphere pressure and low temperature has been studied in a cylindrical dielectric barrier discharge (DBD) reactor. Pure CO2 feed flows to the discharge zone and typical filamentary discharges were obtained in each half-cycle of the applied voltage. The gas temperature increased with discharge time and discharge power, which was found to affect the CO2 decomposition deeply. As the DBD reactor was cooled to ambient temperature, both the conversion of CO2 and the CO yield were enhanced. Especially the energy efficiencies changed slightly with the increase of discharge power and were much higher in cooling condition comparing to those without cooling. At a discharge power of 40 W, the energy efficiency under cooling condition was approximately six times more than that without cooling. Gas flow rate was observed to affect CO2 conversion and 0.1 L min-1 was obtained as optimum gas flow rate under cooling condition. In addition, the CO2 conversion rate in plasma/g-C3N4 catalyst hybrid system was twice times as that in plasma-alone system. In case of cooling, the existence of g-C3N4 catalyst contributed to a 47% increase of CO2 conversion compared to the sole plasma process. The maximum energy-efficiency with g-C3N4 was 0.26 mmol kJ-1 at 20 W, which increased by 157% compared to that without g-C3N4. The synergistic effect of DBD plasma with g-C3N4 on pure CO2 conversion was verified.

An extended car-following model with consideration of the electric vehicle's driving range

NASA Astrophysics Data System (ADS)

Tang, Tie-Qiao; Chen, Liang; Yang, Shi-Chun; Shang, Hua-Yan

2015-07-01

In this paper, we propose a car-following model to explore the influences of the electric vehicle's driving range on the driving behavior under four traffic situations. The numerical results illustrate that the electric vehicle's behavior of exchanging battery at the charge station can destroy the stability of traffic flow and produce some prominent jams, and that the influences are related to the electric vehicle's driving range, i.e., the shorter the driving range is, the greater the effects are.

Determining skill transferability of action games as a method to reduce in-vehicle phone distractions.

PubMed

Rupp, M; McConnell, D S; Smither, J A

2012-01-01

Distracted driving has been shown to be a safety issue in numerous studies. To combat this problem, in-vehicle technology, legislation, media interventions, and other methods have been proposed and attempted. However research indicates that the drivers themselves may circumvent, ignore, or not be able to react in time for these interventions to be effective. Therefore research into training programs for drivers may improve reaction time under distraction. Research indicates that action game players have faster reaction times and more attentional resources than non-players on paper-based tests. However, transferability to driving has not been studied yet. This paper outlines a study to determine if action game players perform better at a driving task based on frequency of game-play. Participants will be placed into two groups of play (high vs. low) and tested against two levels of distraction (none vs. phone conversation). It is expected that participants who play higher frequency of action games will perform better under distraction than lower frequency players. Driver performance, conversation recall, frequency and durations of eye fixations will be analyzed based on previous research which has validated those variables as a measure of distraction and higher workload.

Nanoscale triboelectric-effect-enabled energy conversion for sustainably powering portable electronics.

PubMed

Wang, Sihong; Lin, Long; Wang, Zhong Lin

2012-12-12

Harvesting energy from our living environment is an effective approach for sustainable, maintenance-free, and green power source for wireless, portable, or implanted electronics. Mechanical energy scavenging based on triboelectric effect has been proven to be simple, cost-effective, and robust. However, its output is still insufficient for sustainably driving electronic devices/systems. Here, we demonstrated a rationally designed arch-shaped triboelectric nanogenerator (TENG) by utilizing the contact electrification between a polymer thin film and a metal thin foil. The working mechanism of the TENG was studied by finite element simulation. The output voltage, current density, and energy volume density reached 230 V, 15.5 μA/cm(2), and 128 mW/cm(3), respectively, and an energy conversion efficiency as high as 10-39% has been demonstrated. The TENG was systematically studied and demonstrated as a sustainable power source that can not only drive instantaneous operation of light-emitting diodes (LEDs) but also charge a lithium ion battery as a regulated power module for powering a wireless sensor system and a commercial cell phone, which is the first demonstration of the nanogenerator for driving personal mobile electronics, opening the chapter of impacting general people's life by nanogenerators.

Mechanistic understanding of surface plasmon assisted catalysis on a single particle: cyclic redox of 4-aminothiophenol

DOE PAGES

Xu, Ping; Kang, Leilei; Mack, Nathan H.; ...

2013-10-21

We investigate surface plasmon assisted catalysis (SPAC) reactions of 4-aminothiophenol (4ATP) to and back from 4,4'-dimercaptoazobenzene (DMAB) by single particle surface enhanced Raman spectroscopy, using a self-designed gas flow cell to control the reductive/oxidative environment over the reactions. Conversion of 4ATP into DMAB is induced by energy transfer (plasmonic heating) from surface plasmon resonance to 4ATP, where O 2 (as an electron acceptor) is essential and H 2O (as a base) can accelerate the reaction. In contrast, hot electron (from surface plasmon decay) induction drives the reverse reaction of DMAB to 4ATP, where H 2O (or H 2) acts asmore » the hydrogen source. More interestingly, the cyclic redox between 4ATP and DMAB by SPAC approach has been demonstrated. Finally, this SPAC methodology presents a unique platform for studying chemical reactions that are not possible under standard synthetic conditions.« less

Completing the mechanical energy pathways in turbulent Rayleigh-Bénard convection.

PubMed

Gayen, Bishakhdatta; Hughes, Graham O; Griffiths, Ross W

2013-09-20

A new, more complete view of the mechanical energy budget for Rayleigh-Bénard convection is developed and examined using three-dimensional numerical simulations at large Rayleigh numbers and Prandtl number of 1. The driving role of available potential energy is highlighted. The relative magnitudes of different energy conversions or pathways change significantly over the range of Rayleigh numbers Ra ~ 10(7)-10(13). At Ra < 10(7) small-scale turbulent motions are energized directly from available potential energy via turbulent buoyancy flux and kinetic energy is dissipated at comparable rates by both the large- and small-scale motions. In contrast, at Ra ≥ 10(10) most of the available potential energy goes into kinetic energy of the large-scale flow, which undergoes shear instabilities that sustain small-scale turbulence. The irreversible mixing is largely confined to the unstable boundary layer, its rate exactly equal to the generation of available potential energy by the boundary fluxes, and mixing efficiency is 50%.

Efficient Solar Energy Harvesting and Storage through a Robust Photocatalyst Driving Reversible Redox Reactions.

PubMed

Zhou, Yangen; Zhang, Shun; Ding, Yu; Zhang, Leyuan; Zhang, Changkun; Zhang, Xiaohong; Zhao, Yu; Yu, Guihua

2018-06-14

Simultaneous solar energy conversion and storage is receiving increasing interest for better utilization of the abundant yet intermittently available sunlight. Photoelectrodes driving nonspontaneous reversible redox reactions in solar-powered redox cells (SPRCs), which can deliver energy via the corresponding reverse reactions, present a cost-effective and promising approach for direct solar energy harvesting and storage. However, the lack of photoelectrodes having both high conversion efficiency and high durability becomes a bottleneck that hampers practical applications of SPRCs. Here, it is shown that a WO 3 -decorated BiVO 4 photoanode, without the need of extra electrocatalysts, can enable a single-photocatalyst-driven SPRC with a solar-to-output energy conversion efficiency as high as 1.25%. This SPRC presents stable performance over 20 solar energy storage/delivery cycles. The high efficiency and stability are attributed to the rapid redox reactions, the well-matched energy level, and the efficient light harvesting and charge separation of the prepared BiVO 4 . This demonstrated device system represents a potential alternative toward the development of low-cost, durable, and easy-to-implement solar energy technologies. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High Temperature Fusion Reactor Cooling Using Brayton Cycle Based Partial Energy Conversion

NASA Technical Reports Server (NTRS)

Juhasz, Albert J.; Sawicki, Jerzy T.

2003-01-01

For some future space power systems using high temperature nuclear heat sources most of the output energy will be used in other than electrical form, and only a fraction of the total thermal energy generated will need to be converted to electrical work. The paper describes the conceptual design of such a partial energy conversion system, consisting of a high temperature fusion reactor operating in series with a high temperature radiator and in parallel with dual closed cycle gas turbine (CCGT) power systems, also referred to as closed Brayton cycle (CBC) systems, which are supplied with a fraction of the reactor thermal energy for conversion to electric power. Most of the fusion reactor's output is in the form of charged plasma which is expanded through a magnetic nozzle of the interplanetary propulsion system. Reactor heat energy is ducted to the high temperature series radiator utilizing the electric power generated to drive a helium gas circulation fan. In addition to discussing the thermodynamic aspects of the system design the authors include a brief overview of the gas turbine and fan rotor-dynamics and proposed bearing support technology along with performance characteristics of the three phase AC electric power generator and fan drive motor.

High Temperature Fusion Reactor Cooling Using Brayton Cycle Based Partial Energy Conversion

NASA Astrophysics Data System (ADS)

Juhasz, Albert J.; Sawicki, Jerzy T.

2004-02-01

For some future space power systems using high temperature nuclear heat sources most of the output energy will be used in other than electrical form, and only a fraction of the total thermal energy generated will need to be converted to electrical work. The paper describes the conceptual design of such a ``partial energy conversion'' system, consisting of a high temperature fusion reactor operating in series with a high temperature radiator and in parallel with dual closed cycle gas turbine (CCGT) power systems, also referred to as closed Brayton cycle (CBC) systems, which are supplied with a fraction of the reactor thermal energy for conversion to electric power. Most of the fusion reactor's output is in the form of charged plasma which is expanded through a magnetic nozzle of the interplanetary propulsion system. Reactor heat energy is ducted to the high temperature series radiator utilizing the electric power generated to drive a helium gas circulation fan. In addition to discussing the thermodynamic aspects of the system design the authors include a brief overview of the gas turbine and fan rotor-dynamics and proposed bearing support technology along with performance characteristics of the three phase AC electric power generator and fan drive motor.

An efficient supersonic wind tunnel drive system for Mach 2.5 flows

NASA Technical Reports Server (NTRS)

Wolf, Stephen W. D.; Laub, James A.; King, Lyndell S.

1991-01-01

A novel efficient drive system has been developed which provides for the continuous operation of a pitot Mach 2.5 wind tunnel at compression ratios down to 0.625:1. The drive system does not require an overpressure to start, and no hysteresis has been observed. The general design of the proof-of-concept wind tunnel using the new drive system and its modifications are described.

Sequenced drive for rotary valves

DOEpatents

Mittell, Larry C.

1981-01-01

A sequenced drive for rotary valves which provides the benefits of applying rotary and linear motions to the movable sealing element of the valve. The sequenced drive provides a close approximation of linear motion while engaging or disengaging the movable element with the seat minimizing wear and damage due to scrubbing action. The rotary motion of the drive swings the movable element out of the flowpath thus eliminating obstruction to flow through the valve.

Turbidity Currents With Equilibrium Basal Driving Layers: A Mechanism for Long Runout

NASA Astrophysics Data System (ADS)

Luchi, R.; Balachandar, S.; Seminara, G.; Parker, G.

2018-02-01

Turbidity currents run out over 100 km in lakes and reservoirs, and over 1,000 km in the ocean. They do so without dissipating themselves via excess entrainment of ambient water. Existing layer-averaged formulations cannot capture this. We use a numerical model to describe the temporal evolution of a turbidity current toward steady state under condition of zero net sediment flux at the bed. The flow self-partitions itself into two layers. The lower "driving layer" approaches an invariant flow thickness, velocity profile, and suspended sediment concentration profile that sequesters nearly all of the suspended sediment. This layer can continue indefinitely at steady state over a constant bed slope. The upper "driven layer" contains a small fraction of the suspended sediment. The devolution of the flow into these two layers likely allows the driving layer to run out long distances.

Electroosmotic Flow Rectification in Membranes with Asymmetrically Shaped Pores: Effects of Current and Pore Density

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bishop, Gregory W.; Lopez, Marcos M.; Ramiah Rajasekaran, Pradeep

2015-07-09

We have recently demonstrated a new electrokinetic phenomenon—electroosmotic flow rectification in membranes with asymmetrically shaped pores. Flow rectification means that at constant driving force the flow rate in one direction through the membrane is faster than the flow rate in the opposite direction. EOF rectification could be of practical use in microfluidic devices incorporating porous membranes, but additional research is required. We explore here the effects of two key experimental variables—current density used to drive flow through the membrane and membrane pore density—on EOF rectification. We have found that the extent of EOF rectification, as quantified by the rectification ratio,more » increases with increasing current density. In contrast, the rectification ratio decreases with increasing membrane pore density. We propose explanations for these results based on simple EOF and membrane-transport theories.« less

The Effect of Rotor Cruise Tip Speed, Engine Technology and Engine/Drive System RPM on the NASA Large Civil Tiltrotor (LCTR2) Size and Performance

NASA Technical Reports Server (NTRS)

Robuck, Mark; Wilkerson, Joseph; Maciolek, Robert; Vonderwell, Dan

2012-01-01

A multi-year study was conducted under NASA NNA06BC41C Task Order 10 and NASA NNA09DA56C task orders 2, 4, and 5 to identify the most promising propulsion system concepts that enable rotor cruise tip speeds down to 54% of the hover tip speed for a civil tiltrotor aircraft. Combinations of engine RPM reduction and 2-speed drive systems were evaluated. Three levels of engine and the drive system advanced technology were assessed; 2015, 2025 and 2035. Propulsion and drive system configurations that resulted in minimum vehicle gross weight were identified. Design variables included engine speed reduction, drive system speed reduction, technology, and rotor cruise propulsion efficiency. The NASA Large Civil Tiltrotor, LCTR, aircraft served as the base vehicle concept for this study and was resized for over thirty combinations of operating cruise RPM and technology level, quantifying LCTR2 Gross Weight, size, and mission fuel. Additional studies show design sensitivity to other mission ranges and design airspeeds, with corresponding relative estimated operational cost. The lightest vehicle gross weight solution consistently came from rotor cruise tip speeds between 422 fps and 500 fps. Nearly equivalent results were achieved with operating at reduced engine RPM with a single-speed drive system or with a two-speed drive system and 100% engine RPM. Projected performance for a 2025 engine technology provided improved fuel flow over a wide range of operating speeds relative to the 2015 technology, but increased engine weight nullified the improved fuel flow resulting in increased aircraft gross weights. The 2035 engine technology provided further fuel flow reduction and 25% lower engine weight, and the 2035 drive system technology provided a 12% reduction in drive system weight. In combination, the 2035 technologies reduced aircraft takeoff gross weight by 14% relative to the 2015 technologies.

Quasielastic neutron scattering with in situ humidity control: Water dynamics in uranyl fluoride

DOE PAGES

Miskowiec, A.; Kirkegaard, M. C.; Herwig, K. W.; ...

2016-03-04

The authors confirm that water vapor pressure is the driving thermodynamic force for the conversion of the anhydrous structure to [(UO 2F 2)(H 2O)] 7 ∙ (H 2O) 4, and they demonstrate the feasibility of extending this approach to aqueous forms of UO 2F 2+ xH 2O. This method has general applicability to systems in which water content itself is a driving variable for structural or dynamical phase transitions.

Bioelectrocatalytic NAD+/NADH inter-conversion: transformation of an enzymatic fuel cell into an enzymatic redox flow battery.

PubMed

Quah, Timothy; Milton, Ross D; Abdellaoui, Sofiene; Minteer, Shelley D

2017-07-25

Diaphorase and a benzylpropylviologen redox polymer were combined to create a bioelectrode that can both oxidize NADH and reduce NAD + . We demonstrate how bioelectrocatalytic NAD + /NADH inter-conversion can transform a glucose/O 2 enzymatic fuel cell (EFC) with an open circuit potential (OCP) of 1.1 V into an enzymatic redox flow battery (ERFB), which can be rapidly recharged by operation as an EFC.

Numerical simulation of interaction of long-wave disturbances with a shock wave on a wedge for the problem of mode decomposition of supersonic flow oscillations

NASA Astrophysics Data System (ADS)

Kirilovskiy, S. V.; Poplavskaya, T. V.; Tsyryulnikov, I. S.

2016-10-01

This work is aimed at obtaining conversion factors of free stream disturbances from shock wave angle φ, angle of acoustic disturbances distribution θ and Mach number M∞ by solving a problem of interaction of long-wave (with the wavelength λ greater than the model length) free-stream disturbances with a shock wave formed in a supersonic flow around the wedge. Conversion factors at x/λ=0.2 as a ration between amplitude of pressure pulsations on the wedge surface and free stream disturbances amplitude were obtained. Factors of conversion were described by the dependence on angle θ of disturbances distribution, shock wave angle φ and Mach number M∞. These dependences are necessary for solving the problem of mode decomposition of disturbances in supersonic flows in wind tunnels.

Integrating a dual-silicon photoelectrochemical cell into a redox flow battery for unassisted photocharging.

PubMed

Liao, Shichao; Zong, Xu; Seger, Brian; Pedersen, Thomas; Yao, Tingting; Ding, Chunmei; Shi, Jingying; Chen, Jian; Li, Can

2016-05-04

Solar rechargeable flow cells (SRFCs) provide an attractive approach for in situ capture and storage of intermittent solar energy via photoelectrochemical regeneration of discharged redox species for electricity generation. However, overall SFRC performance is restricted by inefficient photoelectrochemical reactions. Here we report an efficient SRFC based on a dual-silicon photoelectrochemical cell and a quinone/bromine redox flow battery for in situ solar energy conversion and storage. Using narrow bandgap silicon for efficient photon collection and fast redox couples for rapid interface charge injection, our device shows an optimal solar-to-chemical conversion efficiency of ∼5.9% and an overall photon-chemical-electricity energy conversion efficiency of ∼3.2%, which, to our knowledge, outperforms previously reported SRFCs. The proposed SRFC can be self-photocharged to 0.8 V and delivers a discharge capacity of 730 mAh l(-1). Our work may guide future designs for highly efficient solar rechargeable devices.

Modeling of the reactant conversion rate in a turbulent shear flow

NASA Technical Reports Server (NTRS)

Frankel, S. H.; Madnia, C. K.; Givi, P.

1992-01-01

Results are presented of direct numerical simulations (DNS) of spatially developing shear flows under the influence of infinitely fast chemical reactions of the type A + B yields Products. The simulation results are used to construct the compositional structure of the scalar field in a statistical manner. The results of this statistical analysis indicate that the use of a Beta density for the probability density function (PDF) of an appropriate Shvab-Zeldovich mixture fraction provides a very good estimate of the limiting bounds of the reactant conversion rate within the shear layer. This provides a strong justification for the implementation of this density in practical modeling of non-homogeneous turbulent reacting flows. However, the validity of the model cannot be generalized for predictions of higher order statistical quantities. A closed form analytical expression is presented for predicting the maximum rate of reactant conversion in non-homogeneous reacting turbulence.

Metallurgical technologies, energy conversion, and magnetohydrodynamic flows

NASA Astrophysics Data System (ADS)

Branover, Herman; Unger, Yeshajahu

The present volume discusses metallurgical applications of MHD, R&D on MHD devices employing liquid working medium for process applications, electromagnetic (EM) modulation of molten metal flow, EM pump performance of superconducting MHD devices, induction EM alkali-metal pumps, a physical model for EM-driven flow in channel-induction furnaces, grain refinement in Al alloys via EM vibrational method, dendrite growth of solidifying metal in dc magnetic field, MHD for mass and heat transfer in single-crystal melt growth, inverse EM shaping, and liquid-metal MHD development in Israel. Also discussed are the embrittlement of steel by lead, an open cycle MHD disk generator, the acceleration of gas-liquid piston flows for molten-metal MHD generators, MHD flow around a cylinder, new MHD drag coefficients, liquid-metal MHD two-phase flow, and two-phase liquid gas mixers for MHD energy conversion. (No individual items are abstracted in this volume)

An alternative arrangement of metered dosing fluid using centrifugal pump

NASA Astrophysics Data System (ADS)

Islam, Md. Arafat; Ehsan, Md.

2017-06-01

Positive displacement dosing pumps are extensively used in various types of process industries. They are widely used for metering small flow rates of a dosing fluid into a main flow. High head and low controllable flow rates make these pumps suitable for industrial flow metering applications. However their pulsating flow is not very suitable for proper mixing of fluids and they are relatively more expensive to buy and maintain. Considering such problems, alternative techniques to control the fluid flow from a low cost centrifugal pump is practiced. These include - throttling, variable speed drive, impeller geometry control and bypass control. Variable speed drive and impeller geometry control are comparatively costly and the flow control by throttling is not an energy efficient process. In this study an arrangement of metered dosing flow was developed using a typical low cost centrifugal pump using bypass flow technique. Using bypass flow control technique a wide range of metered dosing flows under a range of heads were attained using fixed pump geometry and drive speed. The bulk flow returning from the system into the main tank ensures better mixing which may eliminate the need of separate agitators. Comparative performance study was made between the bypass flow control arrangement of centrifugal pump and a diaphragm type dosing pump. Similar heads and flow rates were attainable using the bypass control system compared to the diaphragm dosing pump, but using relatively more energy. Geometrical optimization of the centrifugal pump impeller was further carried out to make the bypass flow arrangement more energy efficient. Although both the systems run at low overall efficiencies but the capital cost could be reduced by about 87% compared to the dosing pump. The savings in capital investment and lower maintenance cost very significantly exceeds the relatively higher energy cost of the bypass system. This technique can be used as a cost effective solution for industries in Bangladesh and have been implemented in two salt iodization plants at Narayangang.

Cold-air performance of compressor-drive turbine of Department of Energy upgraded automobile gas turbine engine. 1: Volute-manifold and stator performance

NASA Technical Reports Server (NTRS)

Roelke, R. J.; Haas, J. E.

1981-01-01

The aerodynamic performance of the inlet manifold and stator assembly of the compressor drive turbine was experimentally determined with cold air as the working fluid. The investigation included measurements of mass flow and stator-exit fluid torque as well as radial surveys of total pressure and flow angle at the stator inlet and annulus surveys of total pressure and flow angle at the stator exit. The stator-exit aftermixed flow conditions and overall stator efficiency were obtained and compared with their design values and the experimental results from three other stators. In addition, an analysis was made to determine the constituent aerodynamic losses that made up the stator kinetic energy loss.

Novel CRISPR/Cas9 gene drive constructs reveal insights into mechanisms of resistance allele formation and drive efficiency in genetically diverse populations

PubMed Central

Liu, Chen

2017-01-01

A functioning gene drive system could fundamentally change our strategies for the control of vector-borne diseases by facilitating rapid dissemination of transgenes that prevent pathogen transmission or reduce vector capacity. CRISPR/Cas9 gene drive promises such a mechanism, which works by converting cells that are heterozygous for the drive construct into homozygotes, thereby enabling super-Mendelian inheritance. Although CRISPR gene drive activity has already been demonstrated, a key obstacle for current systems is their propensity to generate resistance alleles, which cannot be converted to drive alleles. In this study, we developed two CRISPR gene drive constructs based on the nanos and vasa promoters that allowed us to illuminate the different mechanisms by which resistance alleles are formed in the model organism Drosophila melanogaster. We observed resistance allele formation at high rates both prior to fertilization in the germline and post-fertilization in the embryo due to maternally deposited Cas9. Assessment of drive activity in genetically diverse backgrounds further revealed substantial differences in conversion efficiency and resistance rates. Our results demonstrate that the evolution of resistance will likely impose a severe limitation to the effectiveness of current CRISPR gene drive approaches, especially when applied to diverse natural populations. PMID:28727785

Understanding the impact of flow rate and recycle on the conversion of a complex biorefinery stream using a flow-through microbial electrolysis cell

DOE PAGES

Lewis, Alex J.; Borole, Abhijeet P.

2016-06-16

We investigated the effect of flow rate and recycle on the conversion of a biomass-derived pyrolysis aqueous phase in amicrobial electrolysis cell (MEC) to demonstrate production of renewable hydrogen in biorefinery. A continuous MEC operation was investigated under one-pass and recycle conditions usingthe complex, biomass-derived, fermentable, mixed substrate feed at a constant concentration of 0.026 g/L,while testing flow rates ranging from 0.19 to 3.6 mL/min. This corresponds to an organic loading rate (OLR) of 0.54₋10 g/L-day. Mass transfer issues observed at low flow rates were alleviated using high flow rates.Increasing the flow rate to 3.6 mL/min (3.7 min HRT) duringmore » one-pass operation increased the hydrogen productivity 3-fold, but anode conversion efficiency (ACE) decreased from 57.9% to 9.9%. Recycle of the anode liquid helped to alleviate kinetic limitations and the ACE increased by 1.8-fold and the hydrogen productivity by 1.2-fold compared to the one-pass condition at the flow rate of 3.6 mL/min (10 g/L-d OLR). High COD removal was also achieved under recycle conditions, reaching 74.2 1.1%, with hydrogen production rate of 2.92 ± 0.51 L/L-day. This study demonstrates the advantages of combining faster flow rates with a recycle process to improve rate of hydrogen production from a switchgrass-derived stream in the biorefinery.« less

Integrated driver modelling considering state transition feature for individual adaptation of driver assistance systems

NASA Astrophysics Data System (ADS)

Raksincharoensak, Pongsathorn; Khaisongkram, Wathanyoo; Nagai, Masao; Shimosaka, Masamichi; Mori, Taketoshi; Sato, Tomomasa

2010-12-01

This paper describes the modelling of naturalistic driving behaviour in real-world traffic scenarios, based on driving data collected via an experimental automobile equipped with a continuous sensing drive recorder. This paper focuses on the longitudinal driving situations which are classified into five categories - car following, braking, free following, decelerating and stopping - and are referred to as driving states. Here, the model is assumed to be represented by a state flow diagram. Statistical machine learning of driver-vehicle-environment system model based on driving database is conducted by a discriminative modelling approach called boosting sequential labelling method.

Transverse ac-driven and geometric ratchet effects for vortices in conformal crystal pinning arrays

DOE PAGES

Reichhardt, Charles; Reichhardt, Cynthia Jane Olsen

2016-02-11

A conformal pinning array is created by taking a conformal transformation of a uniform hexagonal lattice to create a structure in which the sixfold ordering of the original lattice is preserved but which has a spatial gradient in the pinning site density. With a series of conformal arrays it is possible to create asymmetric substrates, and it was previously shown that when an ac drive is applied parallel to the asymmetry direction, a pronounced ratchet effect occurs with a net dc flow of vortices in the same direction as the ac drive. Here, in this article, we show that whenmore » the ac drive is applied perpendicular to the substrate asymmetry direction, it is possible to realize a transverse ratchet effect where a net dc flow of vortices is generated perpendicular to the ac drive. The conformal transverse ratchet effect is distinct from previous versions of transverse ratchets in that it occurs due to the generation of non-Gaussian transverse vortex velocity fluctuations by the plastic motion of vortices, so that the system behaves as a noise correlation ratchet. The transverse ratchet effect is much more pronounced in the conformal arrays than in random gradient arrays and is absent in square gradient arrays due the different nature of the vortex flow in each geometry. We show that a series of reversals can occur in the transverse ratchet effect due to changes in the vortex flow across the pinning gradient as a function of vortex filling, pinning strength, and ac amplitude. We also consider the case where a dc drive applied perpendicular to the substrate asymmetry direction generates a net flow of vortices perpendicular to the dc drive, producing what is known as a geometric or drift ratchet that again arises due to non-Gaussian dynamically generated fluctuations. The drift ratchet is more efficient than the ac driven ratchet and also exhibits a series of reversals for varied parameters. Lastly, our results should be general to a wide class of systems undergoing nonequilibrium dynamics on conformal substrates, such as colloidal particles on optical traps.« less

14 CFR 23.955 - Fuel flow.

Code of Federal Regulations, 2010 CFR

2010-01-01

... STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Powerplant Fuel System § 23.955 Fuel flow. (a) General. The ability of the fuel system to provide fuel at the rates specified in this... drive flow, and for all other purposes for which fuel is used. (b) Gravity systems. The fuel flow rate...

14 CFR 23.955 - Fuel flow.

Code of Federal Regulations, 2013 CFR

2013-01-01

... STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Powerplant Fuel System § 23.955 Fuel flow. (a) General. The ability of the fuel system to provide fuel at the rates specified in this... drive flow, and for all other purposes for which fuel is used. (b) Gravity systems. The fuel flow rate...

14 CFR 23.955 - Fuel flow.

Code of Federal Regulations, 2012 CFR

2012-01-01

... STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Powerplant Fuel System § 23.955 Fuel flow. (a) General. The ability of the fuel system to provide fuel at the rates specified in this... drive flow, and for all other purposes for which fuel is used. (b) Gravity systems. The fuel flow rate...

14 CFR 23.955 - Fuel flow.

Code of Federal Regulations, 2014 CFR

2014-01-01

... STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Powerplant Fuel System § 23.955 Fuel flow. (a) General. The ability of the fuel system to provide fuel at the rates specified in this... drive flow, and for all other purposes for which fuel is used. (b) Gravity systems. The fuel flow rate...

14 CFR 23.955 - Fuel flow.

Code of Federal Regulations, 2011 CFR

2011-01-01

... STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Powerplant Fuel System § 23.955 Fuel flow. (a) General. The ability of the fuel system to provide fuel at the rates specified in this... drive flow, and for all other purposes for which fuel is used. (b) Gravity systems. The fuel flow rate...

Pinning, flux diodes and ratchets for vortices interacting with conformal pinning arrays

DOE PAGES

Olson Reichhardt, C. J.; Wang, Y. L.; Xiao, Z. L.; ...

2016-05-31

A conformal pinning array can be created by conformally transforming a uniform triangular pinning lattice to produce a new structure in which the six-fold ordering of the original lattice is conserved but where there is a spatial gradient in the density of pinning sites. Here we examine several aspects of vortices interacting with conformal pinning arrays and how they can be used to create a flux flow diode effect for driving vortices in different directions across the arrays. Under the application of an ac drive, a pronounced vortex ratchet effect occurs where the vortices flow in the easy direction ofmore » the array asymmetry. When the ac drive is applied perpendicular to the asymmetry direction of the array, it is possible to realize a transverse vortex ratchet effect where there is a generation of a dc flow of vortices perpendicular to the ac drive due to the creation of a noise correlation ratchet by the plastic motion of the vortices. We also examine vortex transport in experiments and compare the pinning effectiveness of conformal arrays to uniform triangular pinning arrays. In conclusion, we find that a triangular array generally pins the vortices more effectively at the first matching field and below, while the conformal array is more effective at higher fields where interstitial vortex flow occurs.« less

Nonlinear Large Scale Flow in a Precessing Cylinder and Its Ability To Drive Dynamo Action

NASA Astrophysics Data System (ADS)

Giesecke, André; Vogt, Tobias; Gundrum, Thomas; Stefani, Frank

2018-01-01

We have conducted experimental measurements and numerical simulations of a precession-driven flow in a cylindrical cavity. The study is dedicated to the precession dynamo experiment currently under construction at Helmholtz-Zentrum Dresden-Rossendorf and aims at the evaluation of the hydrodynamic flow with respect to its ability to drive a dynamo. We focus on the strongly nonlinear regime in which the flow is essentially composed of the directly forced primary Kelvin mode and higher modes in terms of standing inertial waves arising from nonlinear self-interactions. We obtain an excellent agreement between experiment and simulation with regard to both flow amplitudes and flow geometry. A peculiarity is the resonance-like emergence of an axisymmetric mode that represents a double roll structure in the meridional plane. Kinematic simulations of the magnetic field evolution induced by the time-averaged flow yield dynamo action at critical magnetic Reynolds numbers around Rmc≈430 , which is well within the range of the planned liquid sodium experiment.

Nonlinear Large Scale Flow in a Precessing Cylinder and Its Ability To Drive Dynamo Action.

PubMed

Giesecke, André; Vogt, Tobias; Gundrum, Thomas; Stefani, Frank

2018-01-12

We have conducted experimental measurements and numerical simulations of a precession-driven flow in a cylindrical cavity. The study is dedicated to the precession dynamo experiment currently under construction at Helmholtz-Zentrum Dresden-Rossendorf and aims at the evaluation of the hydrodynamic flow with respect to its ability to drive a dynamo. We focus on the strongly nonlinear regime in which the flow is essentially composed of the directly forced primary Kelvin mode and higher modes in terms of standing inertial waves arising from nonlinear self-interactions. We obtain an excellent agreement between experiment and simulation with regard to both flow amplitudes and flow geometry. A peculiarity is the resonance-like emergence of an axisymmetric mode that represents a double roll structure in the meridional plane. Kinematic simulations of the magnetic field evolution induced by the time-averaged flow yield dynamo action at critical magnetic Reynolds numbers around Rm^{c}≈430, which is well within the range of the planned liquid sodium experiment.

Hydro-geomechanical behaviour of gas-hydrate bearing soils during gas production through depressurization and CO2 injection

NASA Astrophysics Data System (ADS)

Deusner, C.; Gupta, S.; Kossel, E.; Bigalke, N.; Haeckel, M.

2015-12-01

Results from recent field trials suggest that natural gas could be produced from marine gas hydrate reservoirs at compatible yields and rates. It appears, from a current perspective, that gas production would essentially be based on depressurization and, when facing suitable conditions, be assisted by local thermal stimulation or gas hydrate conversion after injection of CO2-rich fluids. Both field trials, onshore in the Alaska permafrost and in the Nankai Trough offshore Japan, were accompanied by different technical issues, the most striking problems resulting from un-predicted geomechanical behaviour, sediment destabilization and catastrophic sand production. So far, there is a lack of experimental data which could help to understand relevant mechanisms and triggers for potential soil failure in gas hydrate production, to guide model development for simulation of soil behaviour in large-scale production, and to identify processes which drive or, further, mitigate sand production. We use high-pressure flow-through systems in combination with different online and in situ monitoring tools (e.g. Raman microscopy, MRI) to simulate relevant gas hydrate production scenarios. Key components for soil mechanical studies are triaxial systems with ERT (Electric resistivity tomography) and high-resolution local strain analysis. Sand production control and management is studied in a novel hollow-cylinder-type triaxial setup with a miniaturized borehole which allows fluid and particle transport at different fluid injection and flow conditions. Further, the development of a large-scale high-pressure flow-through triaxial test system equipped with μ-CT is ongoing. We will present results from high-pressure flow-through experiments on gas production through depressurization and injection of CO2-rich fluids. Experimental data are used to develop and parametrize numerical models which can simulate coupled process dynamics during gas-hydrate formation and gas production.

Effects on wetting by spray on concentrated flow erosion and intake rate

USDA-ARS?s Scientific Manuscript database

When water flows in dry rills (or furrows), fast wetting and aggregate slaking occur. Conversely, when rain wets the surface of the soil before applying concentrated flow, slow wetting precedes the concentrated flow, and less aggregate disintegration occurs. It is hypothesized that slow wetting by t...

Energetics of the Brazil Current in the Rio Grande Cone region

NASA Astrophysics Data System (ADS)

Brum, André Lopes; Azevedo, José Luiz Lima de; Oliveira, Leopoldo Rota de; Calil, Paulo Henrique Rezende

2017-10-01

The energetics of the Brazil Current (BC) in the region of the Rio Grande Cone (RGC, 30-35.5°S), a topographic rise in the southwest portion of the Brazilian continental margin, are analyzed using 16 years of numerical data from the Ocean General Circulation Model (OGCM) for the Earth Simulator (OFES). The main focus of this study is the eddy-mean flow interactions of the BC and the local energy budgets in the study region. The kinetic and potential energy balance equations are derived for mean and eddy flows, and the resulting terms are presented and discussed. The eddy-mean flow interactions exhibit complex spatial distributions, and the intensities of the energy budgets decrease with increasing depth. However, only the mean potential energy (MPE) budget decreases southward. Eddy kinetic energy (EKE) and eddy potential energy (EPE) exhibit similar horizontal distribution patterns. Additionally, the baroclinic and barotropic conversion rates increase downstream of the bump, where the eddy energy field exhibits along-stream variability that increases southward. Barotropic conversion is more intense between 50 and 200 m, where mean kinetic energy (MKE) and EKE are concentrated, and it exhibits a horizontal cross-stream variation pattern, with mean-to-eddy energy conversion observed on the offshore side of the BC. This result indicates that the turbulence associated with the stream jet increases as the BC moves away from the coast, with the conversion term acting to stabilize the flow. Baroclinic conversion exhibits a high intensity below 300 m (where MPE and EPE display peaks), and it has a greater influence on the eddy-mean flow interaction than does the barotropic conversion. The RGC directly affects the local dynamics of the BC by increasing the eddy field as soon as the BC reaches the bump. The energy diagrams illustrate a stream characterized by evolving barotropic and baroclinic instability processes throughout the water column. This result indicates an intrinsically unstable jet in the study region. Moreover, baroclinic instability is the main source of EKE in the RGC region.

Off-Design Performance of a Multi-Stage Supersonic Turbine

NASA Technical Reports Server (NTRS)

Dorney, Daniel J.; Griffin, Lisa W.; Huber, Frank; Sondak, Douglas L.

2003-01-01

The drive towards high-work turbines has led to designs which can be compact, transonic, supersonic, counter rotating, or use a dense drive gas. These aggressive designs can lead to strong unsteady secondary flows and flow separation. The amplitude and extent of these unsteady flow phenomena can be amplified at off-design operating conditions. Pre-test off-design predictions have been performed for a new two-stage supersonic turbine design that is currently being tested in air. The simulations were performed using a three-dimensional unsteady Navier-Stokes analysis, and the predicted results have been compared with solutions from a validated meanline analysis.

Characteristics of secondary migration driving force of tight oil and its geologic effect: a case study of Jurassic in Central Sichuan Basin

NASA Astrophysics Data System (ADS)

Pang, Zhenglian; Tao, Shizhen; Zhang, Bin; Wu, Songtao; Yang, Jiajing; Chen, Ruiyin

2017-04-01

As the rising of its production, tight oil is becoming more and more important. Much research has been done about it. Some articles mention that buoyancy is ineffective for tight oil secondary migration, and abnormal pressure is the alternative. Others believe that overpressure caused hydrocarbon generation is the very force. Though opinions have been given, there are two inadequacies. Firstly, the points are lack of sufficient evidences. Mostly, they are only one or two sentences in the papers. Secondly, geologic effect of the change of driving force hasn't been discussed. In this context, analog experiments, physical property testing, mercury injection, and oil/source comparison were utilized to study 3 issues: origin and value of tight oil secondary migration resistance, values and effectiveness of different potential driving forces, and geologic effect of tight oil secondary migration driving force. Firstly, resistance values of tight reservoir were detected by analog experiments. The value of tight limestone is 15.8MPa, while tight sandstone is 10.7MPa. Tiny size of pores and throats in tight reservoir is the main reason causing huge resistances. Over 90% of pores and throats in tight reservoir are smaller than 1μm. They form huge capillary force when oil migrating through them. Secondly, maximum of buoyancy in study area was confirmed, 0.09MPa, too small to overcome the resistances. Meanwhile, production data suggests that tight oil distribution pattern is not controlled by buoyancy. Conversely, analog experiment proves that overpressure caused by hydrocarbon generation can reach 38MPa, large enough to be the driving force. This idea is also supported by positive correlation between output and source rock formation pressure. Thirdly, is the geologic effect of tight oil secondary migration resistance and driving force. Tight oil can migrate only as non-darcy flow due to huge resistances according to percolation experiments. It needs to overcome the starting pressure gradient. As a result, it migrated a much shorter distance compared with conventional petroleum, coincident with the result of oil/source comparison. The effect of driving force is that boundary of tight oil profitable area is controlled by source rock. This boundary in the study area is the line of hydrocarbon generating strength of 40×104t/km2. By confirming controlling factors of tight oil formation and their evaluation index, it is of great significance during tight oil exploration.

Extended Visual Glances Away from the Roadway are Associated with ADHD- and Texting-Related Driving Performance Deficits in Adolescents.

PubMed

Kingery, Kathleen M; Narad, Megan; Garner, Annie A; Antonini, Tanya N; Tamm, Leanne; Epstein, Jeffery N

2015-08-01

The purpose of the research study was to determine whether ADHD- and texting-related driving impairments are mediated by extended visual glances away from the roadway. Sixty-one adolescents (ADHD =28, non-ADHD =33; 62% male; 11% minority) aged 16-17 with a valid driver's license were videotaped while engaging in a driving simulation that included a No Distraction, Hands-Free Phone Conversation, and Texting condition. Two indicators of visual inattention were coded: 1) percentage of time with eyes diverted from the roadway; and 2) number of extended (greater than 2 s) visual glances away from the roadway. Adolescents with ADHD displayed significantly more visual inattention to the roadway on both visual inattention measures. Increased lane position variability among adolescents with ADHD compared to those without ADHD during the Hands-Free Phone Conversation and Texting conditions was mediated by an increased number of extended glances away from the roadway. Similarly, texting resulted in decreased visual attention to the roadway. Finally, increased lane position variability during texting was also mediated by the number of extended glances away from the roadway. Both ADHD and texting impair visual attention to the roadway and the consequence of this visual inattention is increased lane position variability. Visual inattention is implicated as a possible mechanism for ADHD- and texting-related deficits and suggests that driving interventions designed to address ADHD- or texting-related deficits in adolescents need to focus on decreasing extended glances away from the roadway.

What Drives Apostates and Converters? The Social and Familial Antecedents of Religious Change among Adolescents

PubMed Central

Longo, Gregory S.; Kim-Spoon, Jungmeen

2015-01-01

While research on the psychology of religion and spirituality has examined religious conversion, little research has examined social and familial variables that might play a role in conversion in adolescence. Longitudinal work examining concurrent conversion experiences – as opposed to retrospective reports – is particularly rare. In an examination of 209 parent-adolescent dyads, findings suggested that those who became religious at Time 2 had higher social competence at Time 1 than did apostates, whereas adolescents who were religious at both times had higher social competence, parent communication, and parent trust than apostates. Additionally, those who converted to their parent’s religion at Time 2 were higher than apostates in Time 1 social competence and parent communication. Results point to the importance of considering social and familial factors in religious conversion. PMID:25664141

Energy Conversion and Storage Requirements for Hybrid Electric Aircraft

NASA Technical Reports Server (NTRS)

Misra, Ajay

2016-01-01

Among various options for reducing greenhouse gases in future large commercial aircraft, hybrid electric option holds significant promise. In the hybrid electric aircraft concept, gas turbine engine is used in combination with an energy storage system to drive the fan that propels the aircraft, with gas turbine engine being used for certain segments of the flight cycle and energy storage system being used for other segments. The paper will provide an overview of various energy conversion and storage options for hybrid electric aircraft. Such options may include fuel cells, batteries, super capacitors, multifunctional structures with energy storage capability, thermoelectric, thermionic or a combination of any of these options. The energy conversion and storage requirements for hybrid electric aircraft will be presented. The role of materials in energy conversion and storage systems for hybrid electric aircraft will be discussed.

Development of a novel parallel-spool pilot operated high-pressure solenoid valve with high flow rate and high speed

NASA Astrophysics Data System (ADS)

Dong, Dai; Li, Xiaoning

2015-03-01

High-pressure solenoid valve with high flow rate and high speed is a key component in an underwater driving system. However, traditional single spool pilot operated valve cannot meet the demands of both high flow rate and high speed simultaneously. A new structure for a high pressure solenoid valve is needed to meet the demand of the underwater driving system. A novel parallel-spool pilot operated high-pressure solenoid valve is proposed to overcome the drawback of the current single spool design. Mathematical models of the opening process and flow rate of the valve are established. Opening response time of the valve is subdivided into 4 parts to analyze the properties of the opening response. Corresponding formulas to solve 4 parts of the response time are derived. Key factors that influence the opening response time are analyzed. According to the mathematical model of the valve, a simulation of the opening process is carried out by MATLAB. Parameters are chosen based on theoretical analysis to design the test prototype of the new type of valve. Opening response time of the designed valve is tested by verifying response of the current in the coil and displacement of the main valve spool. The experimental results are in agreement with the simulated results, therefore the validity of the theoretical analysis is verified. Experimental opening response time of the valve is 48.3 ms at working pressure of 10 MPa. The flow capacity test shows that the largest effective area is 126 mm2 and the largest air flow rate is 2320 L/s. According to the result of the load driving test, the valve can meet the demands of the driving system. The proposed valve with parallel spools provides a new method for the design of a high-pressure valve with fast response and large flow rate.

Driving of Dramatic Geomagnetic Activity by Enhancement of Meso-Scale Polar-cap Flows

NASA Astrophysics Data System (ADS)

Lyons, L. R.; Gallardo-Lacourt, B.; Zou, Y.; Nishimura, Y.; Anderson, P. C.; Angelopoulos, V.; Ruohoniemi, J. M.; Mitchell, E. J.; Paxton, L. J.; Nishitani, N.

2017-12-01

Recent studies have shown that mesoscale flows are common within the polar cap ionosphere. They often cross the magnetic separatrix, and become are critical to the driving of geomagnetic activity. They lead, for example, to plasma sheet flow bursts, auroral poleward boundary intensifications, auroral streamers, substorms, auroral omega bands, and poleward motion of the polar cap boundary from reconnection. We have found large enhancements of these meso-scale ionospheric polar cap flows heading towards the nightside separatrix. These enhancements are common immediately after the impact of CME shocks under southward IMF, but can also occur in other situations, including without substantial change in the solar wind or IMF. These meso-scale flow enhancements, which must extent outward along magnetospheric field lines from the ionosphere, are seen to drive an almost immediate strong auroral, ionospheric and field-aligned current, and reconnection activity. The resulting activity is particularly dramatic during the initiation of CME storms, but may reflect a more generally occurring phenomenon of mesoscale flow enhancements leading to similar oval responses without a shock impact, including during and following the expansion phase some substorms. If this phenomenon is indeed common, it could lead to possibly fundamental questions, such as when do polar cap convection enhancements lead to a substorm growth phase versus leading directly to strong poleward expansion of, and strong activity within, the auroral oval field line region? Another critical question would be what leads to and causes the enhancements in meso-scale polar cap flows?

A numerical study of circulation driven by mixing over a submarine bank

NASA Astrophysics Data System (ADS)

Cummins, Patrick F.; Foreman, Michael G. G.

1998-04-01

A primitive equation model is applied to study the spin-up of a linearly stratified, rotating fluid over an isolated topographic bank. The model has vertical eddy mixing coefficients that decay away from the bottom over a specified e-folding scale. No external flows are imposed, and a circulation develops due solely to diffusion over the sea bed. Vertical mixing, coupled with the condition of zero diffusive flux of heat through the sea floor, leads to a distortion of isothermal surfaces near the bottom. The associated radial pressure gradients drive a radial-overturning circulation with upslope flow just above the bottom and downslope flows at greater height. Coriolis forces on the radial flows accelerate a verticallysheared azimuthal (alongslope) circulation. Near the bottom the azimuthal motion is cyclonic (upwelling favourable), while outside the boundary layer, the motion is anticyclonic. Sensitivity experiments show that this pattern is robust and maintained even with constant mixing coefficients. Attention is given to the driving mechanism for the depth-averaged azimuthal motion. An analysis of the relative angular momentum balance determines that the torque associated with bottom stresses drives the anticyclonic depth-averaged flow. In terms of vorticity, the anticyclonic vortex over the bank arises due to the curl of bottom stress divided by the depth. A parameter sensitivity study indicates that the depth-averaged flow is relatively insensitive to variations in the bottom drag coefficient.

Quantifying Hydrate Formation in Gas-rich Environments Using the Method of Characteristics

NASA Astrophysics Data System (ADS)

You, K.; Flemings, P. B.; DiCarlo, D. A.

2015-12-01

Methane hydrates hold a vast amount of methane globally, and have huge energy potential. Methane hydrates in gas-rich environments are the most promising production targets. We develop a one-dimensional analytical solution based on the method of characteristics to explore hydrate formation in such environments (Figure 1). Our solution shows that hydrate saturation is constant with time and space in a homogeneous system. Hydrate saturation is controlled by the initial thermodynamic condition of the system, and changed by the gas fractional flow. Hydrate saturation increases with the initial distance from the hydrate phase boundary. Different gas fractional flows behind the hydrate solidification front lead to different gas saturations at the hydrate solidification front. The higher the gas saturation at the front, the less the volume available to be filled by hydrate, and hence the lower the hydrate saturation. The gas fractional flow depends on the relative permeability curves, and the forces that drive the flow. Viscous forces (the drive for flow induced from liquid pressure gradient) dominate the flow, and hydrate saturation is independent on the gas supply rates and the flow directions at high gas supply rates. Hydrate saturation can be estimated as one minus the ratio of the initial to equilibrium salinity. Gravity forces (the drive for flow induced from the gravity) dominate the flow, and hydrate saturation depends on the flow rates and the flow directions at low gas supply rates. Hydrate saturation is highest for upward flow, and lowest for downward flow. Hydrate saturation decreases with the flow rate for upward flow, and increases with the flow rate for downward flow. This analytical solution illuminates how hydrate is formed by gas (methane, CO2, ethane, propane) flowing into brine-saturated sediments at both the laboratory and geological scales (Figure 1). It provides an approach to generalize the understanding of hydrate solidification in gas-rich environments, although complicated numerical models have been developed previously. Examples of gas expulsion into hydrate stability zones and the associated hydrate formation in both laboratory and geological scales, and CO2 sequestration into CO2-hydrates near the seafloor and under the permafrost will be presented.

The ejector flowmeter as air/oxygen mixing device. An apparatus providing gas mixtures with adjustable oxygen content for high-flow humidification systems.

PubMed

Christensen, K N; Waaben, J; Jørgensen, S

1980-04-01

The ejector flowmeter is constructed for continuous removal of excess gas from anaesthetic circuits. This instrument can be used as an air/oxygen mixing device for high-flow humidification systems in wards where compressed air is not available. Pure oxygen is used as driving gas through the ejector. A nomogram has been constructed to show the relationship between oxygen driving pressure, inlet of air to the flowmeter, FIO2 and total outflow.

Stochastic fundamental diagram for probabilistic traffic flow modeling.

DOT National Transportation Integrated Search

2011-09-01

Flowing water in river, transported gas or oil in pipe, electric current in wire, moving : goods on conveyor, molecular motors in living cell, and driving vehicles on a highway are : various kinds of flow from physical or non-physical systems, yet ea...

Self-Regulation of E×B Flow Shear via Plasma Turbulence

NASA Astrophysics Data System (ADS)

Vianello, N.; Spada, E.; Antoni, V.; Spolaore, M.; Serianni, G.; Regnoli, G.; Cavazzana, R.; Bergsåker, H.; Drake, J. R.

2005-04-01

The momentum balance has been applied to the E×B flow in the edge region of a reversed field pinch (RFP) configuration. All terms, including those involving fluctuations, have been measured in stationary condition in the edge region of the Extrap-T2R RFP experiment. It is found that the component of the Reynolds stress driven by electrostatic fluctuations is the term playing the major role in driving the shear of the E×B flow to a value marginal for turbulent suppression, so that the results are in favor of a turbulence self-regulating mechanism underlying the momentum balance at the edge. Balancing the sheared flow driving and damping terms, the plasma viscosity is found anomalous and consistent with the diffusivity due to electrostatic turbulence.

Self-regulation of E x B flow shear via plasma turbulence.

PubMed

Vianello, N; Spada, E; Antoni, V; Spolaore, M; Serianni, G; Regnoli, G; Cavazzana, R; Bergsåker, H; Drake, J R

2005-04-08

The momentum balance has been applied to the ExB flow in the edge region of a reversed field pinch (RFP) configuration. All terms, including those involving fluctuations, have been measured in stationary condition in the edge region of the Extrap-T2R RFP experiment. It is found that the component of the Reynolds stress driven by electrostatic fluctuations is the term playing the major role in driving the shear of the ExB flow to a value marginal for turbulent suppression, so that the results are in favor of a turbulence self-regulating mechanism underlying the momentum balance at the edge. Balancing the sheared flow driving and damping terms, the plasma viscosity is found anomalous and consistent with the diffusivity due to electrostatic turbulence.

Particle Transport and Size Sorting in Bubble Microstreaming Flow

NASA Astrophysics Data System (ADS)

Thameem, Raqeeb; Rallabandi, Bhargav; Wang, Cheng; Hilgenfeldt, Sascha

2014-11-01

Ultrasonic driving of sessile semicylindrical bubbles results in powerful steady streaming flows that are robust over a wide range of driving frequencies. In a microchannel, this flow field pattern can be fine-tuned to achieve size-sensitive sorting and trapping of particles at scales much smaller than the bubble itself; the sorting mechanism has been successfully described based on simple geometrical considerations. We investigate the sorting process in more detail, both experimentally (using new parameter variations that allow greater control over the sorting) and theoretically (incorporating the device geometry as well as the superimposed channel flow into an asymptotic theory). This results in optimized criteria for size sorting and a theoretical description that closely matches the particle behavior close to the bubble, the crucial region for size sorting.

Using particle tracking to measure flow instabilities in an undergraduate laboratory experiment

NASA Astrophysics Data System (ADS)

Kelley, Douglas H.; Ouellette, Nicholas T.

2011-03-01

Much of the drama and complexity of fluid flow occurs because its governing equations lack unique solutions. The observed behavior depends on the stability of the multitude of solutions, which can change with the experimental parameters. Instabilities cause sudden global shifts in behavior. We have developed a low-cost experiment to study a classical fluid instability. By using an electromagnetic technique, students drive Kolmogorov flow in a thin fluid layer and measure it quantitatively with a webcam. They extract positions and velocities from movies of the flow using Lagrangian particle tracking and compare their measurements to several theoretical predictions, including the effect of the drive current, the spatial structure of the flow, and the parameters at which instability occurs. The experiment can be tailored to undergraduates at any level or to graduate students by appropriate emphasis on the physical phenomena and the sophisticated mathematics that govern them.

Methods and apparatus for carbon dioxide removal from a fluid stream

DOEpatents

Wei, Wei; Ruud, James Anthony; Ku, Anthony Yu-Chung; Ramaswamy, Vidya; Liu, Ke

2010-01-19

An apparatus for producing hydrogen gas wherein the apparatus includes a reactor. In one embodiment, the reactor includes at least two conversion-removal portions. Each conversion-removal portion comprises a catalyst section configured to convert CO in the stream to CO.sub.2 and a membrane section located downstream of and in flow communication with the catalyst section. The membrane section is configured to selectively remove the CO.sub.2 from the stream and to be in flow communication with a sweep gas.

A qualitative exploration of driving stress and driving discourtesy.

PubMed

Scott-Parker, B; Jones, C M; Rune, K; Tucker, J

2018-05-31

Driving courtesy, and conversely driving discourtesy, recently has been of great interest in the public domain. In addition, there has been increasing recognition of the negative impact of stress upon the individual's health and wellbeing, with a plethora of interventions aimed at minimising stress more generally. The research literature regarding driving dis/courtesy, in comparison, is scant, with a handful of studies examining the dis/courteous driving behaviour of road users, and the relationship between driving discourtesy and driving stress. To examine courteous and discourteous driving experiences, and to explore the impact of stress associated with such driving experiences. Thirty-eight drivers (20 females) from the Sunshine Coast region volunteered to participate in one of four 1-1.5 h focus groups. Content analysis used the verbatim utterances captured via an Mp3 device. Three themes pertaining to stressful and discourteous interactions were identified. Theme one pertained to the driving context: road infrastructure (eg, roundabouts, roadwork), vehicles (eg, features), location (eg, country vs city, unfamiliar areas), and temporal aspects (eg, holidays). Theme two pertained to other road users: their behaviour (eg, tailgating, merging), and unknown factors (eg, illicit and licit drug use). Theme three pertained to the self as road user: their own behaviours (eg, deliberate intimidation), and their emotions (eg, angry reaction to other drivers, being in control). Driving dis/courtesy and driving stress is a complex phenomenon, suggesting complex intervention efforts are required. Driving discourtesy was reported as being highly stressful, therefore intervention efforts which encourage driving courtesy and which foster emotional capacity to cope with stressful circumstances appear warranted. Copyright © 2018. Published by Elsevier Ltd.

Fast charge separation in a non-fullerene organic solar cell with a small driving force

NASA Astrophysics Data System (ADS)

Liu, Jing; Chen, Shangshang; Qian, Deping; Gautam, Bhoj; Yang, Guofang; Zhao, Jingbo; Bergqvist, Jonas; Zhang, Fengling; Ma, Wei; Ade, Harald; Inganäs, Olle; Gundogdu, Kenan; Gao, Feng; Yan, He

2016-07-01

Fast and efficient charge separation is essential to achieve high power conversion efficiency in organic solar cells (OSCs). In state-of-the-art OSCs, this is usually achieved by a significant driving force, defined as the offset between the bandgap (Egap) of the donor/acceptor materials and the energy of the charge transfer (CT) state (ECT), which is typically greater than 0.3 eV. The large driving force causes a relatively large voltage loss that hinders performance. Here, we report non-fullerene OSCs that exhibit ultrafast and efficient charge separation despite a negligible driving force, as ECT is nearly identical to Egap. Moreover, the small driving force is found to have minimal detrimental effects on charge transfer dynamics of the OSCs. We demonstrate a non-fullerene OSC with 9.5% efficiency and nearly 90% internal quantum efficiency despite a low voltage loss of 0.61 V. This creates a path towards highly efficient OSCs with a low voltage loss.

Development of Wave Turbine Emulator in a Laboratory Environment

NASA Astrophysics Data System (ADS)

Vinatha, U.; Vittal K, P.

2013-07-01

Wave turbine emulator (WTE) is an important equipment for developing wave energy conversion system. The emulator reflects the actual behavior of the wave turbine by reproducing the characteristics of real wave turbine without reliance on natural wave resources and actual wave turbine. It offers a controllable test environment that allows the evaluation and improvement of control schemes for electric generators. The emulator can be used for research applications to drive an electrical generator in a similar way as a practical wave turbine. This article presents the development of a WTE in a laboratory environment and studies on the behavior of electrical generator coupled to the emulator. The structure of a WTE consists of a PC where the characteristics of the turbine are implemented, ac drive to emulate the turbine rotor, feedback mechanism from the drive and power electronic equipment to control the drive. The feedback signal is acquired by the PC through an A/D converter, and the signal for driving the power electronic device comes from the PC through a D/A converter.

Solutal Marangoni flows of miscible liquids drive transport without surface contamination

NASA Astrophysics Data System (ADS)

Kim, Hyoungsoo; Muller, Koen; Shardt, Orest; Afkhami, Shahriar; Stone, Howard A.

2017-11-01

Mixing and spreading of different liquids are omnipresent in nature, life and technology, such as oil pollution on the sea, estuaries, food processing, cosmetic and beverage industries, lab-on-a-chip devices, and polymer processing. However, the mixing and spreading mechanisms for miscible liquids remain poorly characterized. Here, we show that a fully soluble liquid drop deposited on a liquid surface remains as a static lens without immediately spreading and mixing, and simultaneously a Marangoni-driven convective flow is generated, which are counterintuitive results when two liquids have different surface tensions. To understand the dynamics, we develop a theoretical model to predict the finite spreading time and length scales, the Marangoni-driven convection flow speed, and the finite timescale to establish the quasi-steady state for the Marangoni flow. The fundamental understanding of this solutal Marangoni flow may enable driving bulk flows and constructing an effective drug delivery and surface cleaning approach without causing surface contamination by immiscible chemical species.

Hybrid bioinorganic approach to solar-to-chemical conversion.

PubMed

Nichols, Eva M; Gallagher, Joseph J; Liu, Chong; Su, Yude; Resasco, Joaquin; Yu, Yi; Sun, Yujie; Yang, Peidong; Chang, Michelle C Y; Chang, Christopher J

2015-09-15

Natural photosynthesis harnesses solar energy to convert CO2 and water to value-added chemical products for sustaining life. We present a hybrid bioinorganic approach to solar-to-chemical conversion in which sustainable electrical and/or solar input drives production of hydrogen from water splitting using biocompatible inorganic catalysts. The hydrogen is then used by living cells as a source of reducing equivalents for conversion of CO2 to the value-added chemical product methane. Using platinum or an earth-abundant substitute, α-NiS, as biocompatible hydrogen evolution reaction (HER) electrocatalysts and Methanosarcina barkeri as a biocatalyst for CO2 fixation, we demonstrate robust and efficient electrochemical CO2 to CH4 conversion at up to 86% overall Faradaic efficiency for ≥ 7 d. Introduction of indium phosphide photocathodes and titanium dioxide photoanodes affords a fully solar-driven system for methane generation from water and CO2, establishing that compatible inorganic and biological components can synergistically couple light-harvesting and catalytic functions for solar-to-chemical conversion.

Hybrid bioinorganic approach to solar-to-chemical conversion

PubMed Central

Nichols, Eva M.; Gallagher, Joseph J.; Liu, Chong; Su, Yude; Resasco, Joaquin; Yu, Yi; Sun, Yujie; Yang, Peidong; Chang, Michelle C. Y.; Chang, Christopher J.

2015-01-01

Natural photosynthesis harnesses solar energy to convert CO2 and water to value-added chemical products for sustaining life. We present a hybrid bioinorganic approach to solar-to-chemical conversion in which sustainable electrical and/or solar input drives production of hydrogen from water splitting using biocompatible inorganic catalysts. The hydrogen is then used by living cells as a source of reducing equivalents for conversion of CO2 to the value-added chemical product methane. Using platinum or an earth-abundant substitute, α-NiS, as biocompatible hydrogen evolution reaction (HER) electrocatalysts and Methanosarcina barkeri as a biocatalyst for CO2 fixation, we demonstrate robust and efficient electrochemical CO2 to CH4 conversion at up to 86% overall Faradaic efficiency for ≥7 d. Introduction of indium phosphide photocathodes and titanium dioxide photoanodes affords a fully solar-driven system for methane generation from water and CO2, establishing that compatible inorganic and biological components can synergistically couple light-harvesting and catalytic functions for solar-to-chemical conversion. PMID:26305947

Analysis of Peristaltic Waves & their Role in Migrating Physarum Plasmodia

NASA Astrophysics Data System (ADS)

Lewis, Owen; Guy, Robert

2017-11-01

The true slime mold Physarum polycephalum exhibits a vast array of sophisticated manipulations of its intracellular cytoplasm. Growing microplasmodia of physarum have been observed to adopt an elongated tadpole shape, then contract in a rhythmic, traveling wave pattern that resembles peristaltic pumping. This contraction drives a fast flow of non-gelated cytoplasm along the cell longitudinal axis. It has been hypothesized that this flow of cytoplasm is a driving factor in generating motility of the plasmodium. In this work, we use two different mathematical models to investigate how peristaltic pumping within physarum may be used to drive cellular motility. We compare the relative phase of flow and deformation waves predicted by both models to similar phase data collected from in vivo experiments using physarum plasmodia. Both models suggest that a mechanical asymmetry in the cell is required to reproduce the experimental observations. Such a mechanical asymmetry is also shown to increase the potential for cellular migration, as measured by both stress generation and migration velocity.

Functional architecture of an optic flow-responsive area that drives horizontal eye movements in zebrafish.

PubMed

Kubo, Fumi; Hablitzel, Bastian; Dal Maschio, Marco; Driever, Wolfgang; Baier, Herwig; Arrenberg, Aristides B

2014-03-19

Animals respond to whole-field visual motion with compensatory eye and body movements in order to stabilize both their gaze and position with respect to their surroundings. In zebrafish, rotational stimuli need to be distinguished from translational stimuli to drive the optokinetic and the optomotor responses, respectively. Here, we systematically characterize the neural circuits responsible for these operations using a combination of optogenetic manipulation and in vivo calcium imaging during optic flow stimulation. By recording the activity of thousands of neurons within the area pretectalis (APT), we find four bilateral pairs of clusters that process horizontal whole-field motion and functionally classify eleven prominent neuron types with highly selective response profiles. APT neurons are prevalently direction selective, either monocularly or binocularly driven, and hierarchically organized to distinguish between rotational and translational optic flow. Our data predict a wiring diagram of a neural circuit tailored to drive behavior that compensates for self-motion. Copyright © 2014 Elsevier Inc. All rights reserved.

Process for preparing a chemical compound enriched in isotope content

DOEpatents

Michaels, Edward D.

1982-01-01

A process to prepare a chemical enriched in isotope content which includes: (a) A chemical exchange reaction between a first and second compound which yields an isotopically enriched first compound and an isotopically depleted second compound; (b) the removal of a portion of the first compound as product and the removal of a portion of the second compound as spent material; (c) the conversion of the remainder of the first compound to the second compound for reflux at the product end of the chemical exchange reaction region; (d) the conversion of the remainder of the second compound to the first compound for reflux at the spent material end of the chemical exchange region; and the cycling of the additional chemicals produced by one conversion reaction to the other conversion reaction, for consumption therein. One of the conversion reactions is an oxidation reaction, and the energy that it yields is used to drive the other conversion reaction, a reduction. The reduction reaction is carried out in a solid polymer electrolyte electrolytic reactor. The overall process is energy efficient and yields no waste by-products.

Differences between emissions measured in urban driving and certification testing of heavy-duty diesel engines

NASA Astrophysics Data System (ADS)

Dixit, Poornima; Miller, J. Wayne; Cocker, David R.; Oshinuga, Adewale; Jiang, Yu; Durbin, Thomas D.; Johnson, Kent C.

2017-10-01

Emissions from eight heavy-duty diesel trucks (HDDTs) equipped with three different exhaust aftertreatment systems (ATS) for controlling nitrogen oxide (NOx) emissions were quantified on a chassis dynamometer using driving schedules representative of stop-and-go and free-flow driving in metropolitan areas. The three control technologies were: 1) cooled exhaust gas recirculation (CEGR) plus a diesel particulate filter (DPF); 2) CEGR and DPF plus advanced engine controls; and 3) CEGR and DPF plus selective catalytic reduction with ammonia (SCR). Results for all control technologies and driving conditions showed PM emission factors were less than the standard, while selected non-regulated emissions (ammonia, carbonyls, and C4-C12 hydrocarbons) and a greenhouse gas (nitrous oxide) were at measurement detection limits. However, NOx emission factors depended on the control technology, engine calibration, and driving mode. For example, emissions from engines with cooled-exhaust gas recirculation (CEGR) were 239% higher for stop-and-go driving as compared with free-flow. For CEGR plus selective catalytic reduction (SCR), the ratio was 450%. A deeper analysis was carried out with the assumption that emissions measured for a drive cycle on either the chassis or in-use driving would be similar. Applying the same NTE rules to the chassis data showed emissions during stop-and-go driving often exceeded the certification standard and >90% of the driving did not fall within the Not-To-Exceed (NTE) control area suggesting the NTE requirements do not provide sufficient emissions control under in-use conditions. On-road measurement of emissions using the same mobile lab while the vehicle followed a free-flow driving schedule verified the chassis results. These results have implications for scientists who build inventories using certification values instead of real world emission values and for metropolitan populations, who are exposed to elevated emissions. The differences in values between real world emissions and certification cycles should be narrowed. For example, one might use a different mix of cold and hot start testing to greater emphasize low temperature/load operation, a separate cycle to specifically characterize low-load operation, or broaden the in-use compliance testing requirements and associated conformity factors to incorporate a wider envelope of vehicle operation, especially at low load conditions. .

Land Change Trends in the Great Plains: Linkages to Climate Variability and Socioeconomic Drivers

NASA Astrophysics Data System (ADS)

Drummond, M. A.

2009-12-01

Land use and land cover change have complex linkages to climate variability and change, socioeconomic driving forces, and land management challenges. To assess these land change dynamics and their driving forces in the Great Plains, we compare and contrast contemporary land conversion across seventeen ecoregions using Landsat remote sensing data and statistical analysis. Large area change analysis in agricultural regions is often hampered by the potential for substantial change detection error and the tendency for land conversions to occur in relatively small patches at the local level. To facilitate a regional scale analysis, a statistical sampling design of randomly selected 10-km by 10-km blocks is used in order to efficiently identify the types and rates of land conversions for four time periods between 1972 and 2000, stratified by relatively homogenous ecoregions. Results show a range of rates and processes of land change that vary by ecoregion contingent on the prevailing interactions between socioeconomic and environmental factors such as climate variability, water availability, and land quality. Ecoregions have differential climate and biophysical advantages for agricultural production and other land use change. Human actions further strengthen or dampen the characteristics of change through farm policy, technological advances, economic opportunities, population and demographic shifts, and surface and groundwater irrigation.

EEG acquisition system based on active electrodes with common-mode interference suppression by Driving Right Leg circuit.

PubMed

Guermandi, Marco; Bigucci, Alessandro; Franchi Scarselli, Eleonora; Guerrieri, Roberto

2015-01-01

We present a system for the acquisition of EEG signals based on active electrodes and implementing a Driving Right Leg circuit (DgRL). DgRL allows for single-ended amplification and analog-to-digital conversion, still guaranteeing a common mode rejection in excess of 110 dB. This allows the system to acquire high-quality EEG signals essentially removing network interference for both wet and dry-contact electrodes. The front-end amplification stage is integrated on the electrode, minimizing the system's sensitivity to electrode contact quality, cable movement and common mode interference. The A/D conversion stage can be either integrated in the remote back-end or placed on the head as well, allowing for an all-digital communication to the back-end. Noise integrated in the band from 0.5 to 100 Hz is comprised between 0.62 and 1.3 μV, depending on the configuration. Current consumption for the amplification and A/D conversion of one channel is 390 μA. Thanks to its low noise, the high level of interference suppression and its quick setup capabilities, the system is particularly suitable for use outside clinical environments, such as in home care, brain-computer interfaces or consumer-oriented applications.

Impact of flows on ion temperatures inferred from neutron spectra in asymmetrically driven OMEGA DT implosions

NASA Astrophysics Data System (ADS)

Gatu Johnson, M.; Frenje, J.; Lahmann, B.; Seguin, F.; Petrasso, R.; Appelbe, B.; Chittenden, J.; Walsh, C.; Delettrez, J.; Igumenshchev, I.; Knauer, J. P.; Glebov, V. Yu.; Forrest, C.; Grimble, W.; Marshall, F.; Michel, T.; Stoeckl, C.; Haines, B. M.; Zylstra, A. B.

2017-10-01

Ion temperatures (Tion) in Inertial Confinement Fusion (ICF) experiments have traditionally been inferred from the broadening of primary neutron spectra. Directional motion (flow) of the fuel at burn, expected to arise due to asymmetries imposed by e.g. engineering features or drive non-uniformity, also impacts broadening and may lead to artificially inflated ``Tion'' values. Flow due to low-mode asymmetries is expected to give rise to line-of-sight variations in measured Tion, as observed in OMEGA cryogenic DT implosions but not in similar experiments at the NIF. In this presentation, we report on OMEGA experiments with intentional drive asymmetry designed for testing the ability to accurately predict and measure line-of-sight differences in apparent Tion due to low-mode asymmetry-seeded flows. The measurements are contrasted to CHIMERA, RAGE and ASTER simulations, providing insight into implosion dynamics and the relative importance of laser drive non-uniformity, stalk and offset as sources of asymmetry. The results highlight the complexity of hot-spot dynamics, which is a problem that must be mastered to achieve ICF ignition. This work was supported in part by the U.S. DOE, NLUF and LLE.

Integrating a dual-silicon photoelectrochemical cell into a redox flow battery for unassisted photocharging

PubMed Central

Liao, Shichao; Zong, Xu; Seger, Brian; Pedersen, Thomas; Yao, Tingting; Ding, Chunmei; Shi, Jingying; Chen, Jian; Li, Can

2016-01-01

Solar rechargeable flow cells (SRFCs) provide an attractive approach for in situ capture and storage of intermittent solar energy via photoelectrochemical regeneration of discharged redox species for electricity generation. However, overall SFRC performance is restricted by inefficient photoelectrochemical reactions. Here we report an efficient SRFC based on a dual-silicon photoelectrochemical cell and a quinone/bromine redox flow battery for in situ solar energy conversion and storage. Using narrow bandgap silicon for efficient photon collection and fast redox couples for rapid interface charge injection, our device shows an optimal solar-to-chemical conversion efficiency of ∼5.9% and an overall photon–chemical–electricity energy conversion efficiency of ∼3.2%, which, to our knowledge, outperforms previously reported SRFCs. The proposed SRFC can be self-photocharged to 0.8 V and delivers a discharge capacity of 730 mAh l−1. Our work may guide future designs for highly efficient solar rechargeable devices. PMID:27142885

The effects of vortex structure and vortex translation on the tropical cyclone boundary layer wind field

NASA Astrophysics Data System (ADS)

Williams, Gabriel J.

2015-03-01

The effects of vortex translation and radial vortex structure in the distribution of boundary layer winds in the inner core of mature tropical cyclones are examined using a high-resolution slab model and a multilevel model. It is shown that the structure and magnitude of the wind field (and the corresponding secondary circulation) depends sensitively on the radial gradient of the gradient wind field above the boundary layer. Furthermore, it is shown that vortex translation creates low wave number asymmetries in the wind field that rotate anticyclonically with height. A budget analysis of the steady state wind field for both models was also performed in this study. Although the agradient force drives the evolution of the boundary layer wind field for both models, it is shown that the manner in which the boundary layer flow responds to this force differs between the two model representations. In particular, the inner core boundary layer flow in the slab model is dominated by the effects of horizontal advection and horizontal diffusion, leading to the development of shock structures in the model. Conversely, the inner core boundary layer flow in the multilevel model is primarily influenced by the effects of vertical advection and vertical diffusion, which eliminates shock structures in this model. These results further indicate that special care is required to ensure that qualitative applications from slab models are not unduly affected by the neglect of vertical advection. This article was corrected on 31 MAR 2015. See the end of the full text for details.

The Formation of Ethane from Carbon Dioxide under Cold Plasma

NASA Astrophysics Data System (ADS)

Zhang, Xiu-ling; Zhang, Lin; Dai, Bin; Gong, Wei-min; Liu, Chang-hou

2001-04-01

Pulsed-corona plasma has been used as a new method for ethane dehydrogenation at low temperature and normal pressure using carbon dioxide as an oxidant in this paper. The effect of carbon dioxide content in the feed, power input, and flow rate of the reactants on the ethane dehydrogenation has been investigated. The experimental results show that the conversion of ethane increases with the increase in the amount of carbon dioxide in the feed. The yield of ethylene and acetylene decreases with the increase in the yield of carbon monoxide, indicating that the increased carbon dioxide leads to the part of ethylene and acetylene being oxidized to carbon monoxide. Power input is primarily an electrical parameter in pulsed-corona plasma, which plays an important role in reactant conversion and product formation. When the power input reaches 16 W, ethane conversion is 41.0% and carbon dioxide conversion is 26.3%. The total yield of ethylene and acetylene is 15.6%. The reduced flow rate of feed improves the conversion of ethane, carbon dioxide and the yield of acetylene, and induces carbon deposit as well.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shaw, B. H.; Applied Science and Technology, University of California, Berkeley, California 94720; Tilborg, J. van

Solid-based surface high-harmonic generation from a tape is experimentally studied. By operating at mildly relativistic normalized laser strengths a{sub 0}≲0.2, harmonics up to the 17th order are efficiently produced in the coherent wake emission (CWE) regime. CWE pulse properties, such as divergence, energy, conversion efficiency, and spectrum, are investigated for various tape materials and drive laser conditions. A clear correlation between surface roughness and harmonic beam divergence is found. At the measured pulse properties for the 15th harmonic (conversion efficiency ∼6.5×10{sup −7}, divergence ∼7−15 mrad), the 100-mJ-level drive laser produces several MWs of extreme ultra-violet pulses. The spooling tape configurationmore » enables multi-Hz operation over thousands of shots, making this source attractive as a seed to the few-Hz laser-plasma-accelerator-driven free-electron laser (FEL). Models indicate that these CWE pulses with MW level powers are sufficient for seed-induced bunching and FEL gain.« less

Semiconducting Single-Walled Carbon Nanotubes in Solar Energy Harvesting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blackburn, Jeffrey L.

Semiconducting single-walled carbon nanotubes (s-SWCNTs) represent a tunable model one-dimensional system with exceptional optical and electronic properties. High-throughput separation and purification strategies have enabled the integration of s-SWCNTs into a number of optoelectronic applications, including photovoltaics (PVs). In this Perspective, we discuss the fundamental underpinnings of two model PV interfaces involving s-SWCNTs. We first discuss s-SWCNT-fullerene heterojunctions where exciton dissociation at the donor-acceptor interface drives solar energy conversion. Next, we discuss charge extraction at the interface between s-SWCNTs and a photoexcited perovskite active layer. In each case, the use of highly enriched semiconducting SWCNT samples enables fundamental insights into themore » thermodynamic and kinetic mechanisms that drive the efficient conversion of solar photons into long-lived separated charges. As a result, these model systems help to establish design rules for next-generation PV devices containing well-defined organic semiconductor layers and help to frame a number of important outstanding questions that can guide future studies.« less

Semiconducting Single-Walled Carbon Nanotubes in Solar Energy Harvesting

DOE PAGES

Blackburn, Jeffrey L.

2017-06-14

Semiconducting single-walled carbon nanotubes (s-SWCNTs) represent a tunable model one-dimensional system with exceptional optical and electronic properties. High-throughput separation and purification strategies have enabled the integration of s-SWCNTs into a number of optoelectronic applications, including photovoltaics (PVs). In this Perspective, we discuss the fundamental underpinnings of two model PV interfaces involving s-SWCNTs. We first discuss s-SWCNT-fullerene heterojunctions where exciton dissociation at the donor-acceptor interface drives solar energy conversion. Next, we discuss charge extraction at the interface between s-SWCNTs and a photoexcited perovskite active layer. In each case, the use of highly enriched semiconducting SWCNT samples enables fundamental insights into themore » thermodynamic and kinetic mechanisms that drive the efficient conversion of solar photons into long-lived separated charges. As a result, these model systems help to establish design rules for next-generation PV devices containing well-defined organic semiconductor layers and help to frame a number of important outstanding questions that can guide future studies.« less

Chromatic effect in a novel THz generation scheme

NASA Astrophysics Data System (ADS)

Li, Bin; Zhang, Wenyan; Liu, Xiaoqing; Deng, Haixiao; Lan, Taihe; Liu, Bo; Liu, Jia; Wang, Xingtao; Zeng, Zhinan; Zhang, Lijian

2017-11-01

Deriving single or few cycle terahertz (THz) pulse by an intense femtosecond laser through cascaded optical rectification is a crucial technique in cutting-edge time-resolved spectroscopy to characterize micro-scale structures and ultrafast dynamics. Due to the broadband nature of the ultrafast driving laser, the chromatic effect limits the THz conversion efficiency in optical rectification crystals, especially for those implementing the pulse-front tilt scheme, e.g. lithium niobate (LN) crystal, has been prevalently used in the past decade. In this research we developed a brand new type of LN crystal utilizing Brewster coupling, and conducted systematically experimental and simulative investigation for the chromatic effect and multi-dimensionally entangled parameters in THz generation, predicting that an extreme conversion efficiency of ˜10% would be potentially achievable at the THz absorption coefficient of ˜0.5 cm-1. Moreover, we first discovered that the chirp of the driving laser plays a decisive role in the pulse-front tilt scheme, and the THz generation efficiency could be enhanced tremendously by applying an appropriate chirp.

Regional dynamics of grassland change in the western Great Plains

USGS Publications Warehouse

Drummond, M.A.

2007-01-01

This paper examines the contemporary land-cover changes in two western Great Plains ecoregions between 1973 and 2000. Agriculture and other land uses can have a substantial effect on grassland cover that varies regionally depending on the primary driving forces of change. In order to better understand change, the rates, types, and causes of land conversion were examined for 1973, 1980, 1986, 1992, and 2000 using Landsat satellite data and a statistical sampling strategy. The overall estimated rate of land-cover change between 1973 and 2000 was 7.4% in the Northwestern Great Plains and 11.5% in the Western High Plains. Trends in both ecoregions have similarities, although the dynamics of change differ temporally depending on driving forces. Between 1973 and 1986, grassland cover declined when economic opportunity drove an expansion of agriculture. Between 1986 and 2000, grassland expanded as public policy and a combination of socioeconomic factors drove a conversion from agriculture to grassland. ?? 2007 Copyright by the Center for Great Plains Studies, University of Nebraska-Lincoln.

Anemometer calibrator

NASA Technical Reports Server (NTRS)

Bate, T.; Calkins, D. E.; Price, P.; Veikins, O.

1971-01-01

Calibrator generates accurate flow velocities over wide range of gas pressure, temperature, and composition. Both pressure and flow velocity can be maintained within 0.25 percent. Instrument is essentially closed loop hydraulic system containing positive displacement drive.

Concerns with AED conversion: comparison of patient and physician perspectives.

PubMed

Smith, Brien J; St Louis, Erik K; Stern, John M; Green, Chad; Bramley, Thomas

2009-06-01

When discussing AED conversion in the clinic, both the patient and physician perspectives on the goals and risks of this change are important to consider. To identify patient-reported and clinician-perceived concerns, a panel of epilepsy specialists was questioned about the topics discussed with patients and the clinician's perspective of patient concerns. Findings of a literature review of articles that report patient-expressed concerns regarding their epilepsy and treatment were also reviewed. Results showed that the specialist panel appropriately identified patient-reported concerns of driving ability, medication cost, seizure control, and medication side effects. Additionally, patient-reported concerns of independence, employment issues, social stigma, medication dependence, and undesirable cognitive effects are important to address when considering and initiating AED conversion.

Flow in E-learning: What Drives It and Why It Matters

ERIC Educational Resources Information Center

Rodríguez-Ardura, Inma; Meseguer-Artola, Antoni

2017-01-01

This paper seeks to explain why some individuals sink further into states of flow than others, and what effects flow has in the context of a virtual education environment. Our findings--gathered from both questionnaire and behavioural data--reveal that flow states are elicited by the e-learners' senses of controlling the virtual education…

Increasing synchrony of high temperature and low flow in western North American streams: Double trouble for coldwater biota?

Treesearch

Ivan Arismendi; Mohammad Safeeq; Sherri L. Johnson; Jason B Dunham; Roy Haggerty

2013-01-01

Flow and temperature are strongly linked environmental factors driving ecosystem processes in streams. Stream temperature maxima (Tmax_w) and stream flow minima (Qmin) can create periods of stress for aquatic organisms. In mountainous areas, such as western North America, recent shifts toward an earlier spring peak flow and...

Towards a universal description of cohesive-particle flows

NASA Astrophysics Data System (ADS)

Lamarche, Casey; Liu, Peiyuan; Kellogg, Kevin; Lattanzi, Aaron; Hrenya, Christine

2017-11-01

A universal framework for describing cohesive granular flows seems unattainable based on prior works, making a fundamental continuum theory to predict such flows appear unachievable. For the first time, universal behavior of cohesive-grain flows is demonstrated by linking the macroscopic (many-grain) behavior to grain-grain interactions via two dimensionless groups: a generalized Bond number BoG - ratio of maximum cohesive force to the force driving flow - and a new Agglomerate number Ag - ratio of critical cohesive energy to the granular energy. Cohesive-grain flow is investigated in several systems, and universal behavior is determined via collapse of a cohesion-dependent output variable from each system with the appropriate dimensionless group. Universal behavior is observed using BoG for dense (enduring-contact-dominated) flows and Ag for dilute (collision-dominated) flows, as BoG accounts for the cohesive contact force and Ag for increased collisional dissipation due to cohesion. Hence, a new physical picture is presented, namely, BoG dominates in dense flows, where force chains drive momentum transfer, and Ag dominates in dilute systems, where the dissipative collisions dominate momentum transfer. Apparent discrepancies with past treatments are resolved. Dow Corning Corporation.

Tendency to occupy a statistically dominant spatial state of the flow as a driving force for turbulent transition.

PubMed

Chekmarev, Sergei F

2013-03-01

The transition from laminar to turbulent fluid motion occurring at large Reynolds numbers is generally associated with the instability of the laminar flow. On the other hand, since the turbulent flow characteristically appears in the form of spatially localized structures (e.g., eddies) filling the flow field, a tendency to occupy such a structured state of the flow cannot be ruled out as a driving force for turbulent transition. To examine this possibility, we propose a simple analytical model that treats the flow as a collection of localized spatial structures, each of which consists of elementary cells in which the behavior of the particles (atoms or molecules) is uncorrelated. This allows us to introduce the Reynolds number, associating it with the ratio between the total phase volume for the system and that for the elementary cell. Using the principle of maximum entropy to calculate the most probable size distribution of the localized structures, we show that as the Reynolds number increases, the elementary cells group into the localized structures, which successfully explains turbulent transition and some other general properties of turbulent flows. An important feature of the present model is that a bridge between the spatial-statistical description of the flow and hydrodynamic equations is established. We show that the basic assumptions underlying the model, i.e., that the particles are indistinguishable and elementary volumes of phase space exist in which the state of the particles is uncertain, are involved in the derivation of the Navier-Stokes equation. Taking into account that the model captures essential features of turbulent flows, this suggests that the driving force for the turbulent transition is basically the same as in the present model, i.e., the tendency of the system to occupy a statistically dominant state plays a key role. The instability of the flow at high Reynolds numbers can then be a mechanism to initiate structural rearrangement of the flow to find this state.

Acceleration of the highest energy cosmic rays through proton-neutron conversions in relativistic bulk flows

NASA Astrophysics Data System (ADS)

Derishev, E.; Aharonian, F.

We show that, in the presence of radiation field, relativistic bulk flows can very quikly accelerate protons and electrons up to the energies limited either by Hillas criterion or by synchrotron losses. Unlike the traditional approach, we take advantage of continuous photon-induced conversion of charged particle species to neutral ones, and vice versa (proton-neutron or electron-photon). Such a conversion, though it leads to considerable energy losses, allows accelerated particles to increase their energies in each scattering by a factor roughly equal to the bulk Lorentz factor, thus avoiding the need in slow and relatively inefficient diffusive acceleration. The optical depth of accelerating region with respect to inelastic photon-induced reactions (pair production for electrons and photomeson reactions for protons) should be a substancial fraction of unity. Remarkably, self-tuning of the optical depth is automatically achieved as long as the photon density depends on the distance along the bulk flow. This mechanism can work in Gamma-Ray Bursts (GRBs), Active Galactic Nuclei (AGNs), microquasars, or any other object with relativistic bulk flows embedded in radiation-reach environment. Both GRBs and AGNs turn out to be capable of producing 1020 eV cosmic rays.

Optimization of a new flow design for solid oxide cells using computational fluid dynamics modelling

NASA Astrophysics Data System (ADS)

Duhn, Jakob Dragsbæk; Jensen, Anker Degn; Wedel, Stig; Wix, Christian

2016-12-01

Design of a gas distributor to distribute gas flow into parallel channels for Solid Oxide Cells (SOC) is optimized, with respect to flow distribution, using Computational Fluid Dynamics (CFD) modelling. The CFD model is based on a 3d geometric model and the optimized structural parameters include the width of the channels in the gas distributor and the area in front of the parallel channels. The flow of the optimized design is found to have a flow uniformity index value of 0.978. The effects of deviations from the assumptions used in the modelling (isothermal and non-reacting flow) are evaluated and it is found that a temperature gradient along the parallel channels does not affect the flow uniformity, whereas a temperature difference between the channels does. The impact of the flow distribution on the maximum obtainable conversion during operation is also investigated and the obtainable overall conversion is found to be directly proportional to the flow uniformity. Finally the effect of manufacturing errors is investigated. The design is shown to be robust towards deviations from design dimensions of at least ±0.1 mm which is well within obtainable tolerances.

Generation of parasitic axial flow by drift wave turbulence with broken symmetry: Theory and experiment

NASA Astrophysics Data System (ADS)

Hong, R.; Li, J. C.; Hajjar, R.; Chakraborty Thakur, S.; Diamond, P. H.; Tynan, G. R.

2018-05-01

Detailed measurements of intrinsic axial flow generation parallel to the magnetic field in the controlled shear decorrelation experiment linear plasma device with no axial momentum input are presented and compared to theory. The results show a causal link from the density gradient to drift-wave turbulence with broken spectral symmetry and development of the axial mean parallel flow. As the density gradient steepens, the axial and azimuthal Reynolds stresses increase and radially sheared azimuthal and axial mean flows develop. A turbulent axial momentum balance analysis shows that the axial Reynolds stress drives the radially sheared axial mean flow. The turbulent drive (Reynolds power) for the azimuthal flow is an order of magnitude greater than that for axial flow, suggesting that the turbulence fluctuation levels are set by azimuthal flow shear regulation. The direct energy exchange between axial and azimuthal mean flows is shown to be insignificant. Therefore, the axial flow is parasitic to the turbulence-zonal flow system and is driven primarily by the axial turbulent stress generated by that system. The non-diffusive, residual part of the axial Reynolds stress is found to be proportional to the density gradient and is formed due to dynamical asymmetry in the drift-wave turbulence.

Flow modeling and permeability estimation using borehole flow logs in heterogeneous fractured formations

USGS Publications Warehouse

Paillet, Frederick L.

1998-01-01

A numerical model of flow in the vicinity of a borehole is used to analyze flowmeter data obtained with high-resolution flowmeters. The model is designed to (1) precisely compute flow in a borehole, (2) approximate the effects of flow in surrounding aquifers on the measured borehole flow, (3) allow for an arbitrary number (N) of entry/exit points connected to M < N far-field aquifers, and (4) be consistent with the practical limitations of flowmeter measurements such as limits of resolution, typical measurement error, and finite measurement periods. The model is used in three modes: (1) a quasi-steady pumping mode where there is no ambient flow, (2) a steady flow mode where ambient differences in far-field water levels drive flow between fracture zones in the borehole, and (3) a cross-borehole test mode where pumping in an adjacent borehole drives flow in the observation borehole. The model gives estimates of transmissivity for any number of fractures in steady or quasi-steady flow experiments that agree with straddle-packer test data. Field examples show how these cross-borehole-type curves can be used to estimate the storage coefficient of fractures and bedding planes and to determine whether fractures intersecting a borehole at different locations are hydraulically connected in the surrounding rock mass.

Theory of ion Bernstein wave induced shear suppression of turbulence

NASA Astrophysics Data System (ADS)

Craddock, G. G.; Diamond, P. H.; Ono, M.; Biglari, H.

1994-06-01

The theory of radio frequency induced ion Bernstein wave- (IBW) driven shear flow in the edge is examined, with the goal of application of shear suppression of fluctuations. This work is motivated by the observed confinement improvement on IBW heated tokamaks [Phys. Fluids B 5, 241 (1993)], and by previous low-frequency work on RF-driven shear flows [Phys. Rev. Lett. 67, 1535 (1991)]. It is found that the poloidal shear flow is driven electrostatically by both Reynolds stress and a direct ion momentum source, analogous to the concepts of helicity injection and electron momentum input in current drive, respectively. Flow drive by the former does not necessarily require momentum input to the plasma to induce a shear flow. For IBW, the direct ion momentum can be represented by direct electron momentum input, and a charge separation induced stress that imparts little momentum to the plasma. The derived Er profile due to IBW predominantly points inward, with little possibility of direction change, unlike low-frequency Alfvénic RF drive. The profile scale is set by the edge density gradient and electron dissipation. Due to the electrostatic nature of ion Bernstein waves, the poloidal flow contribution dominates in Er. Finally, the necessary edge power absorbed for shear suppression on Princeton Beta Experiment-Modified (PBX-M) [9th Topical Conference on Radio Frequency Power in Plasmas, Charleston, SC, 1991 (American Institute of Physics, New York, 1991), p. 129] is estimated to be 100 kW distributed over 5 cm.

Rapid Microfluidic Mixers Utilizing Dispersion Effect and Interactively Time-Pulsed Injection

NASA Astrophysics Data System (ADS)

Leong, Jik-Chang; Tsai, Chien-Hsiung; Chang, Chin-Lung; Lin, Chiu-Feng; Fu, Lung-Ming

2007-08-01

In this paper, we present a novel active microfluidic mixer utilizing a dispersion effect in an expansion chamber and applying interactively time-pulsed driving voltages to the respective inlet fluid flows to induce electroosmotic flow velocity variations for developing a rapid mixing effect in a microchannel. Without using any additional equipment to induce flow perturbations, only a single high-voltage power source is required for simultaneously driving and mixing sample fluids, which results in a simple and low-cost system for mixing. The effects of the applied main electrical field, interactive frequency, and expansion ratio on the mixing performance are thoroughly examined experimentally and numerically. The mixing ratio can be as high as 95% within a mixing length of 3000 μm downstream from the secondary T-form when a driving electric field strength of 250 V/cm, a periodic switching frequency of 5 Hz, and the expansion ratio M=1:10 are applied. In addition, the optimization of the driving electric field, switching frequency, expansion ratio, expansion entry length, and expansion chamber length for achieving a maximum mixing ratio is also discussed in this study. The novel method proposed in this study can be used for solving the mixing problem in the field of micro-total-analysis systems in a simple manner.

An investigation of driver distraction near the tipping point of traffic flow stability.

PubMed

Cooper, Joel M; Vladisavljevic, Ivana; Medeiros-Ward, Nathan; Martin, Peter T; Strayer, David L

2009-04-01

The purpose of this study was to explore the interrelationship between driver distraction and characteristics of driver behavior associated with reduced highway traffic efficiency. Research on the three-phase traffic theory and on behavioral driving suggests that a number of characteristics associated with efficient traffic flow may be affected by driver distraction. Previous studies have been limited, however, by the fact that researchers typically do not allow participants to change lanes, nor do they account for the impact of varying traffic states on driving performance. Participants drove in three simulated environments with differing traffic congestion while both using and not using a cell phone. Instructed only to obey the speed limit, participants were allowed to vary driving behaviors, such as those involving forward following distance, speed, and lane-changing frequency. Both driver distraction and traffic congestion were found to significantly affect lane change frequency, mean speed, and the likelihood of remaining behind a slower-moving lead vehicle. This research suggests that the behavioral profile of "cell phone drivers," which is often described as compensatory, may have far-reaching and unexpected consequences for traffic efficiency. By considering the dynamic interplay between characteristics of traffic flow and driver behavior, this research may inform both public policy regarding in-vehicle cell phone use and future investigations of driving behavior.

Prototype Development of an Implantable Compliance Chamber for a Total Artificial Heart.

PubMed

Schmitz, Stephanie; Unthan, Kristin; Sedlaczek, Marc; Wald, Felix; Finocchiaro, Thomas; Spiliopoulos, Sotirios; Koerfer, Reiner; Steinseifer, Ulrich

2017-02-01

At our institute a total artificial heart is being developed. It is directly actuated by a linear drive in between two ventricles, which comprise membranes to separate the drive and blood flow. A compliance chamber (CC) is needed to reduce pressure peaks in the ventricles and to increase the pump capacity. Therefore, the movement of the membrane is supported by applying a negative pressure to the air volume inside the drive unit. This study presents the development of the implantable CC which is connected to the drive unit of the total artificial hearts (TAH). The anatomical fit of the CC is optimized by analyzing CT data and adapting the outer shape to ensure a proper fit. The pressure peaks are reduced by the additional volume and the flexible membrane of the CC. The validation measurements of change in pressure peaks and flow are performed using the complete TAH system connected to a custom mock circulation loop. Using the CC, the pressure peaks could be damped below 5 mm Hg in the operational range. The flow output was increased by up to 14.8% on the systemic side and 18.2% on the pulmonary side. The described implantable device can be used for upcoming chronic animal trials. © 2016 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Statistical validation and an empirical model of hydrogen production enhancement found by utilizing passive flow disturbance in the steam-reformation process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Erickson, Paul A.; Liao, Chang-hsien

2007-11-15

A passive flow disturbance has been proven to enhance the conversion of fuel in a methanol-steam reformer. This study presents a statistical validation of the experiment based on a standard 2{sup k} factorial experiment design and the resulting empirical model of the enhanced hydrogen producing process. A factorial experiment design was used to statistically analyze the effects and interactions of various input factors in the experiment. Three input factors, including the number of flow disturbers, catalyst size, and reactant flow rate were investigated for their effects on the fuel conversion in the steam-reformation process. Based on the experimental results, anmore » empirical model was developed and further evaluated with an uncertainty analysis and interior point data. (author)« less

Stop/Start: Driving

Science.gov Websites

/generator visible. The car is moving. There are purple arrows flowing from the gasoline engine to the electric starter/generator. There are red arrows flowing from the gasoline engine to the front wheels . There are blue arrows flowing from the electric starter/generator to the battery. Main stage: See

Energy conversion and dissipation at dipolarization fronts: Theory, modeling and MMS observations

NASA Astrophysics Data System (ADS)

Sitnov, M. I.; Motoba, T.; Merkin, V. G.; Ohtani, S.; Cohen, I. J.; Mauk, B.; Vines, S. K.; Anderson, B. J.; Moore, T. E.; Torbert, R. B.; Giles, B. L.; Burch, J. L.

2017-12-01

Magnetic reconnection is one of the most important energy conversion mechanisms in space plasmas. In the classical picture it converts the energy of antiparallel magnetic fields into the kinetic and thermal energy of accelerated plasma particles in reconnection exhausts. It also involves energy dissipation near the X-line. This classical picture may be substantially modified in real space plasma configurations, such as the dayside magnetopause and the magnetotail. In particular, in the magnetotail the flows of accelerated particles may be strongly asymmetric along the tail with the domination of earthward flows. At the same time, strong energy conversion and even dissipation may occur away from the X-line, in particular, at dipolarization fronts. Here we present a theoretical picture of spontaneous magnetotail reconnection based on 3-D PIC simulations with the focus on plasma bulk flows, energy conversion and dissipation. This picture is compared with some observations from the MMS tail season. An important finding from these observations is that dipolarizations fronts may not only be regions of the total energy conversion with jE>0, but they may also be the sites of energy dissipation, both positive (jE'>0, E' is the electric field E in the system moving with one of the plasma species) and negative (jE'<0). Observations are further compared with theory and modeling that predict the specific location and sign of the energy dissipation at fronts depending on their evolution phase (e.g., formation, propagation, braking).

Extended visual glances away from the roadway are associated with ADHD- and texting-related driving performance deficits in adolescents

PubMed Central

Kingery, Kathleen M.; Narad, Megan; Garner, Annie A.; Antonini, Tanya N.; Tamm, Leanne; Epstein, Jeffery N.

2014-01-01

The purpose of the research study was to determine whether ADHD- and texting-related driving impairments are mediated by extended visual glances away from the roadway. Sixty-one adolescents (ADHD = 28, non-ADHD = 33; 62% male; 11% minority) aged 16–17 with a valid driver’s license were videotaped while engaging in a driving simulation that included a No Distraction, Hands-Free Phone Conversation, and Texting condition. Two indicators of visual inattention were coded: 1) percentage of time with eyes diverted from the roadway; and 2) number of extended (greater than 2 seconds) visual glances away from the roadway. Adolescents with ADHD displayed significantly more visual inattention to the roadway on both visual inattention measures. Increased lane position variability among adolescents with ADHD compared to those without ADHD during the Hands-Free Phone Conversation and Texting conditions was mediated by an increased number of extended glances away from the roadway. Similarly, texting resulted in decreased visual attention to the roadway. Finally, increased lane position variability during texting was also mediated by the number of extended glances away from the roadway. Both ADHD and texting impair visual attention to the roadway and the consequence of this visual inattention is increased lane position variability. Visual inattention is implicated as a possible mechanism for ADHD- and texting-related deficits and suggests that driving interventions designed to address ADHD- or texting-related deficits in adolescents need to focus on decreasing extended glances away from the roadway. PMID:25416444

Cell phone-induced failures of visual attention during simulated driving

DOT National Transportation Integrated Search

2003-01-01

Synopsis This experiment finds that conversing on a hands-free cell phone with a stream of traffic passing in the left lane leads participants to take longer to respond when the car ahead brakes and to a longer time before they reach their slowes...

ELECTRIC VEHICLE CONVERSIONS USING ALTERNATIVE ENERGY TO DRIVE ALASKAN RURAL COMMUNITIES

EPA Science Inventory

This proposal concerns sustainable transportation in rural Alaskan communities which are not part of a road or electrical network (off grid). In most off-grid communities, the road networks generally are less than 50 square miles, so transportation needs are limited. This limi...

Indigenous knowledges driving technological innovation

Treesearch

Lilian Alessa; Carlos Andrade; Phil Cash Cash; Christian P. Giardina; Matt Hamabata; Craig Hammer; Kai Henifin; Lee Joachim; Jay T. Johnson; Kekuhi Kealiikanakaoleohaililani; Deanna Kingston; Andrew Kliskey; Renee Pualani Louis; Amanda Lynch; Daryn McKenny; Chels Marshall; Mere Roberts; Taupouri Tangaro; Jyl Wheaton-Abraham; Everett Wingert

2011-01-01

This policy brief explores the use and expands the conversation on the ability of geospatial technologies to represent Indigenous cultural knowledge. Indigenous peoples' use of geospatial technologies has already proven to be a critical step for protecting tribal self-determination. However, the ontological frameworks and techniques of Western geospatial...

Intraplate deformation, stress in the lithosphere and the driving mechanism for plate motions

NASA Technical Reports Server (NTRS)

Albee, Arden L.

1993-01-01

The initial research proposed was to use the predictions of geodynamical models of mantle flow, combined with geodetic observations of intraplate strain and stress, to better constrain mantle convection and the driving mechanism for plate motions and deformation. It is only now that geodetic observations of intraplate strain are becoming sufficiently well resolved to make them useful for substantial geodynamical inference to be made. A model of flow in the mantle that explains almost 90 percent of the variance in the observed longwavelength nonhydrostatic geoid was developed.

Reverse Flow Engine Core Having a Ducted Fan with Integrated Secondary Flow Blades

NASA Technical Reports Server (NTRS)

Kisska, Michael K. (Inventor); Princen, Norman H. (Inventor); Kuehn, Mark S. (Inventor); Cosentino, Gary B. (Inventor)

2014-01-01

Secondary air flow is provided for a ducted fan having a reverse flow turbine engine core driving a fan blisk. The fan blisk incorporates a set of thrust fan blades extending from an outer hub and a set of integral secondary flow blades extending intermediate an inner hub and the outer hub. A nacelle provides an outer flow duct for the thrust fan blades and a secondary flow duct carries flow from the integral secondary flow blades as cooling air for components of the reverse flow turbine engine.

Investigation of turbines for driving supersonic compressors II : performance of first configuration with 2.2 percent reduction in nozzle flow area / Warner L. Stewart, Harold J. Schum, Robert Y. Wong

NASA Technical Reports Server (NTRS)

Stewart, Warner L; Schum, Harold J; Wong, Robert Y

1952-01-01

The experimental performance of a modified turbine for driving a supersonic compressor is presented and compared with the performance of the original configuration to illustrate the effect of small changes in the ratio of nozzle-throat area to rotor-throat area. Performance is based on the performance of turbines designed to operate with both blade rows close to choking. On the basis of the results of this investigation, the ratio of areas is concluded to become especially critical in the design of turbines such as those designed to drive high-speed, high-specific weight-flow compressors where the turbine nozzles and rotor are both very close to choking.

Mechanical Extraction of Power From Ocean Currents and Tides

NASA Technical Reports Server (NTRS)

Jones, Jack; Chao, Yi

2010-01-01

A proposed scheme for generating electric power from rivers and from ocean currents, tides, and waves is intended to offer economic and environmental advantages over prior such schemes, some of which are at various stages of implementation, others of which have not yet advanced beyond the concept stage. This scheme would be less environmentally objectionable than are prior schemes that involve the use of dams to block rivers and tidal flows. This scheme would also not entail the high maintenance costs of other proposed schemes that call for submerged electric generators and cables, which would be subject to degradation by marine growth and corrosion. A basic power-generation system according to the scheme now proposed would not include any submerged electrical equipment. The submerged portion of the system would include an all-mechanical turbine/pump unit that would superficially resemble a large land-based wind turbine (see figure). The turbine axis would turn slowly as it captured energy from the local river flow, ocean current, tidal flow, or flow from an ocean-wave device. The turbine axis would drive a pump through a gearbox to generate an enclosed flow of water, hydraulic fluid, or other suitable fluid at a relatively high pressure [typically approx.500 psi (approx.3.4 MPa)]. The pressurized fluid could be piped to an onshore or offshore facility, above the ocean surface, where it would be used to drive a turbine that, in turn, would drive an electric generator. The fluid could be recirculated between the submerged unit and the power-generation facility in a closed flow system; alternatively, if the fluid were seawater, it could be taken in from the ocean at the submerged turbine/pump unit and discharged back into the ocean from the power-generation facility. Another alternative would be to use the pressurized flow to charge an elevated reservoir or other pumped-storage facility, from whence fluid could later be released to drive a turbine/generator unit at a time of high power demand. Multiple submerged turbine/pump units could be positioned across a channel to extract more power than could be extracted by a single unit. In that case, the pressurized flows in their output pipes would be combined, via check valves, into a wider pipe that would deliver the combined flow to a power-generating or pumped-storage facility.

Code Conversion Impact Factor and Cash Flow Impact of International Classification of Diseases, 10th Revision, on a Large Multihospital Radiology Practice.

PubMed

Jalilvand, Aryan; Fleming, Margaret; Moreno, Courtney; MacFarlane, Dan; Duszak, Richard

2018-01-01

The 2015 conversion of the International Classification of Diseases (ICD) system from the ninth revision (ICD-9) to the 10th revision (ICD-10) was widely projected to adversely impact physician practices. We aimed to assess code conversion impact factor (CCIF) projections and revenue delay impact to help radiology groups better prepare for eventual conversion to ICD, 11th revision (ICD-11). Studying 673,600 claims for 179 radiologists for the first year after ICD-10's implementation, we identified primary ICD-10 codes for the top 90th percentile of all examinations for the entire enterprise and each subspecialty division. Using established methodology, we calculated CCIFs (actual ICD-10 codes ÷ prior ICD-9 codes). To assess ICD-10's impact on cash flow, average monthly days in accounts receivable status was compared for the 12 months before and after conversion. Of all 69,823 ICD-10 codes, only 7,075 were used to report primary diagnoses across the entire practice, and just 562 were used to report 90% of all claims, compared with 348 under ICD-9. This translates to an overall CCIF of 1.6 for the department (far less than the literature-predicted 6). By subspecialty division, CCIFs ranged from 0.7 (breast) to 3.5 (musculoskeletal). Monthly average days in accounts receivable for the 12 months before and after ICD-10 conversion did not increase. The operational impact of the ICD-10 transition on radiology practices appears far less than anticipated with respect to both CCIF and delays in cash flow. Predictive models should be refined to help practices better prepare for ICD-11. Copyright © 2017 American College of Radiology. Published by Elsevier Inc. All rights reserved.

A New Solution for Confined-Unconfined Flow Toward a Fully Penetrating Well in a Confined Aquifer.

PubMed

Xiao, Liang; Ye, Ming; Xu, Yongxin

2018-02-08

Transient confined-unconfined flow conversion caused by pumping in a confined aquifer (i.e., piezometric head drops below the top confined layer) is complicated, partly due to different hydraulic properties between confined and unconfined regions. For understanding mechanism of the transient confined-unconfined conversion, this paper develops a new analytical solution for the transient confined-unconfined flow toward a fully penetrating well in a confined aquifer. The analytical solution is used to investigate the impacts on drawdown simulation by differences of hydraulic properties, including transmissivity, storativity, and diffusivity defined as a ratio of transmissivity and storativity, between the confined and unconfined regions. It is found that neglecting the transmissivity difference may give an overestimation of drawdown. Instead, neglecting the diffusivity difference may lead to an underestimation of drawdown. The shape of drawdown-time curve is sensitive to the change of storativity ratio, S/S y , between the confined and unconfined regions. With a series of drawdown data from pumping tests, the analytical solution can also be used to inversely estimate following parameters related to the transient confined-unconfined conversion: radial distance of conversion interface, diffusivity, and specific yield of the unconfined region. It is concluded that using constant transmissivity and diffusivity in theory can result in biased estimates of radial distance of the conversion interface and specific yield of the unconfined region in practice. The analytical solution is useful to gain insight about various factors related to the transient confined-unconfined conversion and can be used for the design of mine drainage and groundwater management in the mining area. © 2018, National Ground Water Association.

Optimization of lipase-catalyzed biodiesel by isopropanolysis in a continuous packed-bed reactor using response surface methodology.

PubMed

Chang, Cheng; Chen, Jiann-Hwa; Chang, Chieh-Ming J; Wu, Tsung-Ta; Shieh, Chwen-Jen

2009-10-31

Isopropanolysis reactions were performed using triglycerides with immobilized lipase in a solvent-free environment. This study modeled the degree of isopropanolysis of soybean oil in a continuous packed-bed reactor when Novozym 435 was used as the biocatalyst. Response surface methodology (RSM) and three-level-three-factor Box-Behnken design were employed to evaluate the effects of synthesis parameters, reaction temperature ( degrees C), flow rate (mL/min) and substrate molar ratio of isopropanol to soybean oil, on the percentage molar conversion of biodiesel by transesterification. The results show that flow rate and temperature have a significant effect on the percentage of molar conversion. On the basis of ridge max analysis, the optimum conditions for synthesis were as follows: flow rate 0.1 mL/min, temperature 51.5 degrees C and substrate molar ratio 1:4.14. The predicted value was 76.62+/-1.52% and actual experimental value was 75.62+/-0.81% molar conversion. Moreover, continuous enzymatic process for seven days did not show any appreciable decrease in the percent of molar conversion (75%). This work demonstrates the applicability of lipase catalysis to prepare isopropyl esters by transesterification in solvent-free system with a continuous packed-bed reactor for industrial production.

Symmetry Breaking by Parallel Flow Shear

NASA Astrophysics Data System (ADS)

Li, Jiacong; Diamond, Patrick

2015-11-01

Plasma rotation is important in reducing turbulent transport, suppressing MHD instabilities, and is beneficial to confinement. Intrinsic rotation without an external momentum input is of interest for its plausible application on ITER. k∥ spectrum asymmetry is required for residual Reynolds stress that drives the intrinsic rotation. Parallel flows are reported in linear devices without magnetic shear. In CSDX, parallel flows are mostly peaked in the core [Thakur et al., 2014]; more robust flows and reversed profiles are seen in PANTA [Oldenburger, et al. 2012]. A novel mechanism for symmetry breaking in momentum transport is proposed. Magnetic shear or mean flow profile are not required. A seed parallel flow shear (PFS) sets the sign of residual stress by selecting certain modes to grow faster. The resulted spectrum imbalance leads to a nonzero residual stress, which further drives a parallel flow with ∇n as the free energy source, adding to the shear until saturated by diffusion. Balanced flow gradient is set by Π∥Res /χϕ . Residual stress is calculated for ITG turbulence and collisional drift wave turbulence where electron-ion and electron-neutral collisions are discussed and compared. Numerical simulation is proposed for testing the effect of PFS.

Lubricant dynamics under sliding condition in disk drives

NASA Astrophysics Data System (ADS)

Wu, Lin

2006-07-01

In this paper, we develop a two-dimensional flow model for the lubricant flow dynamics under a sliding head in disk drives. Our two-dimensional model includes important physics such as viscous force, external air shearing stress, air bearing pressure, centrifugal force, disjoining pressure, and surface tension. Our analysis shows that the lubricant flow dynamics under the sliding condition is a fully two-dimensional phenomenon and the circumferential lubricant flow is strongly coupled to the radial flow. It is necessary to have a two-dimensional flow model that couples the circumferential and radial flows together and includes all important physics to achieve realistic predictions. Our results show that the external air shearing stress has a dominant effect on the lubricant flow dynamics. Both velocity slippage at wall and Poiseuille flow effects have to be considered in the evaluation of the air shearing stress under the head. The nonuniform air bearing pressure has a non-negligible effect on the lubricant film dynamics mostly through the Poiseuille flow effect on the air shearing stress but not from its direct pushing or sucking effect on the lubricant surface. Prediction of the formation of lubricant depletion tracks under a sliding head using the two-dimensional model agrees reasonably well with the existing experimental measurements.

System International d'Unites: Metric Measurement in Water Resources Engineering.

ERIC Educational Resources Information Center

Klingeman, Peter C.

This pamphlet gives definitions and symbols for the basic and derived metric units, prefixes, and conversion factors for units frequently used in water resources. Included are conversion factors for units of area, work, heat, power, pressure, viscosity, flow rate, and others. (BB)

Single channel double-duct liquid metal electrical generator using a magnetohydrodynamic device

DOEpatents

Haaland, C.M.; Deeds, W.E.

1999-07-13

A single channel double-duct liquid metal electrical generator using a magnetohydrodynamic (MHD) device. The single channel device provides useful output AC electric energy. The generator includes a two-cylinder linear-piston engine which drives liquid metal in a single channel looped around one side of the MHD device to form a double-duct contra-flowing liquid metal MHD generator. A flow conduit network and drive mechanism are provided for moving liquid metal with an oscillating flow through a static magnetic field to produce useful AC electric energy at practical voltages and currents. Variable stroke is obtained by controlling the quantity of liquid metal in the channel. High efficiency is obtained over a wide range of frequency and power output. 5 figs.

Single channel double-duct liquid metal electrical generator using a magnetohydrodynamic device

DOEpatents

Haaland, Carsten M.; Deeds, W. Edward

1999-01-01

A single channel double-duct liquid metal electrical generator using a magnetohydrodynamic (MHD) device. The single channel device provides useful output AC electric energy. The generator includes a two-cylinder linear-piston engine which drives liquid metal in a single channel looped around one side of the MHD device to form a double-duct contra-flowing liquid metal MHD generator. A flow conduit network and drive mechanism are provided for moving liquid metal with an oscillating flow through a static magnetic field to produce useful AC electric energy at practical voltages and currents. Variable stroke is obtained by controlling the quantity of liquid metal in the channel. High efficiency is obtained over a wide range of frequency and power output.

Time course of pressure and flow in ascending aorta during ejection.

PubMed

Perlini, S; Soldà, P L; Piepoli, M; Calciati, A; Paro, M; Marchetti, G; Meno, F; Finardi, G; Bernardi, L

1991-02-01

To analyze aortic flow and pressure relationships, 10 closed-chest anaesthetised dogs were instrumented with electromagnetic aortic flow probes and micromanometers in the left ventricle and ascending aorta. Left ventricular ejection time was divided into: time to peak flow (T1) (both pressure and flow rising), peak flow to peak pressure time (T2) (pressure rising, flow decreasing), and peak pressure to dicrotic notch time (T3) (pressure and flow both decreasing). These time intervals were expressed as percent of total ejection time. Load-active interventions rose markedly T2 (from 4.2 +/- 5.5 to 19.4 +/- 3.5 after phenylephrine (p less than 0.02); from 4.2 +/- 6.5 to 21.2 +/- 5.3 after dextran (p less than 0.02)). Conversely, dobutamine reduced T2 from 4.4 +/- 5.9 to -2.5 +/- 6.5 (p less than 0.05). Thus, during load-active interventions aortic pressure increases for a longer T2 time although forward flow is decreasing, as a result of higher aortic elastic recoil during ejection. Conversely, beta 1-adrenergic stimulation significantly shortens T2. Dynamic pressure-flow relationship is thus continuously changing during ejection. T2 seems to be inversely related to the efficiency of left ventricular ejection dynamics.

The evolution of sensory divergence in the context of limited gene flow in the bumblebee bat

PubMed Central

Puechmaille, Sébastien J.; Gouilh, Meriadeg Ar; Piyapan, Piyathip; Yokubol, Medhi; Mie, Khin Mie; Bates, Paul J.; Satasook, Chutamas; Nwe, Tin; Bu, Si Si Hla; Mackie, Iain J.; Petit, Eric J.; Teeling, Emma C.

2011-01-01

The sensory drive theory of speciation predicts that populations of the same species inhabiting different environments can differ in sensory traits, and that this sensory difference can ultimately drive speciation. However, even in the best-known examples of sensory ecology driven speciation, it is uncertain whether the variation in sensory traits is the cause or the consequence of a reduction in levels of gene flow. Here we show strong genetic differentiation, no gene flow and large echolocation differences between the allopatric Myanmar and Thai populations of the world's smallest mammal, Craseonycteris thonglongyai, and suggest that geographic isolation most likely preceded sensory divergence. Within the geographically continuous Thai population, we show that geographic distance has a primary role in limiting gene flow rather than echolocation divergence. In line with sensory-driven speciation models, we suggest that in C. thonglongyai, limited gene flow creates the suitable conditions that favour the evolution of sensory divergence via local adaptation. PMID:22146392

Tornado type wind turbines

DOEpatents

Hsu, Cheng-Ting

1984-01-01

A tornado type wind turbine has a vertically disposed wind collecting tower with spaced apart inner and outer walls and a central bore. The upper end of the tower is open while the lower end of the structure is in communication with a wind intake chamber. An opening in the wind chamber is positioned over a turbine which is in driving communication with an electrical generator. An opening between the inner and outer walls at the lower end of the tower permits radially flowing air to enter the space between the inner and outer walls while a vertically disposed opening in the wind collecting tower permits tangentially flowing air to enter the central bore. A porous portion of the inner wall permits the radially flowing air to interact with the tangentially flowing air so as to create an intensified vortex flow which exits out of the top opening of the tower so as to create a low pressure core and thus draw air through the opening of the wind intake chamber so as to drive the turbine.

Revolutionary land use change in the 21st century: Is (rangeland) science relevant?

USDA-ARS?s Scientific Manuscript database

Rapidly increasing demand for food, fiber and fuel together with new technologies and the mobility of global capital are driving revolutionary changes in land use throughout the world. Efforts to increase land productivity include conversion of millions of hectares of rangelands to crop production, ...

Toward Social Justice: Literature to Promote Multiple Perspectives

ERIC Educational Resources Information Center

Gibson, Karen; Parks, Marguerite W.

2014-01-01

The purpose of this article is to investigate the struggles of teacher education students when confronted with establishing a social justice curriculum. The authors' work focuses on using multicultural literature as a starting point for the critical conversations that drive curricular changes. Introducing ideas of culturally responsive pedagogy…

Bi-continuous Multi-component Nanocrystal Superlattices for Solar Energy Conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kagan, Cherie; Murray, Christopher; Kikkawa, James

2017-06-14

Our SISGR program studied an emerging class of nanomaterials wherein different combinations of semiconductor or semiconductor and plasmonic nanocrystals (NCs) are self-assembled into three-dimensional multi-component superlattices. The NC assemblies were designed to form bicontinuous semiconductor NC sublattices with type-II energy offsets to drive charge separation onto electron and hole transporting sublattices for collection and introduce plasmonic NCs to increase solar absorption and charge separation. Our group is expert in synthesizing and assembling an extraordinary variety of artificial systems by tailoring the NC building blocks and the superlattice unit cell geometry. Under this DOE BES Materials Chemistry program, we introduced chemicalmore » methods to control inter-particle distance and to dope NC assemblies, which enabled our demonstration of strong electronic communication between NCs and the use of NC thin films as electronic materials. We synthesized, assembled and structurally, spectroscopically, and electrically probed NC superlattices to understand and manipulate the flow of energy and charge toward discovering the design rules and optimizing these complex architectures to create materials that efficiently convert solar radiation into electricity.« less

Solar energy conversion.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crabtree, G. W.; Lewis, N. S.; Materials Science Division

2007-03-01

The Sun provides Earth with a staggering amount of energy - enough to power the great oceanic and atmospheric currents, the cycle of evaporation and condensation that brings fresh water inland and drives river flow, and the typhoons, hurricanes, and tornadoes that so easily destroy the natural and built landscape. The San Francisco earthquake of 1906, with magnitude 7.8, released an estimated 10{sup 17} joules of energy, the amount the Sun delivers to Earth in one second. Earth's ultimate recoverable resource of oil, estimated at 3 trillion barrels, contains 1.7 x 10{sup 22} joules of energy, which the Sun suppliesmore » to Earth in 1.5 days. The amount of energy humans use annually, about 4.6 x 10{sup 20} joules, is delivered to Earth by the Sun in one hour. The enormous power that the Sun continuously delivers to Earth, 1.2 x 10{sup 5} terawatts, dwarfs every other energy source, renewable or nonrenewable. It dramatically exceeds the rate at which human civilization produces and uses energy, currently about 13 TW.« less

“Are you still driving?” Meta-synthesis of patient preferences for communication with healthcare providers

PubMed Central

Betz, Marian E.; Scott, Kenneth; Jones, Jacqueline; DiGuiseppi, Carolyn

2015-01-01

Aim To synthesize published qualitative studies to identify older adults’ preferences for communication about driving with healthcare providers. Background Healthcare providers play a key role in addressing driving safety and driving retirement with older adults, but conversations about driving can be difficult. Guides exist for family members and providers, but to date less is known about the types of communication and messages older drivers want from their healthcare providers. Design Qualitative metasynthesis of studies published on or before October 10, 2014, in databases (PubMed, CINAHL, PsycINFO and Web of Science) and grey literature. Review Methods 22 published studies representing 518 older adult drivers met the following inclusion criteria: (1) the study was about driving; (2) the study involved older drivers; (3) the study was qualitative (rather than quantitative or mixed methods); and (4) the study contained information on older drivers’ perspectives about communication with healthcare providers. Results We identified five major themes regarding older adults’ communication preferences: (1) driving discussions are emotionally charged; (2) context matters; (3) providers are trusted and viewed as authority figures; (4) communication should occur over a period of time rather than suddenly; and (5) older adults desire agency in the decision to stop driving. Conclusion Various stakeholders involved in older driver safety should consider older drivers’ perspectives regarding discussions about driving. Healthcare providers can respect and empower older drivers—and support their family members—through tactful communication about driving safety and mobility transitions during the life course. PMID:26507251

"Are you still driving?" Metasynthesis of patient preferences for communication with health care providers.

PubMed

Betz, Marian E; Scott, Kenneth; Jones, Jacqueline; Diguiseppi, Carolyn

2016-05-18

The aim of this study was to synthesize published qualitative studies to identify older adults' preferences for communication about driving with health care providers. Health care providers play a key role in addressing driving safety and driving retirement with older adults, but conversations about driving can be difficult. Guides exist for family members and providers, but to date less is known about the types of communication and messages older drivers want from their health care providers. A qualitative metasynthesis of studies published on or before October 10, 2014, in databases (PubMed, CINAHL, PsycINFO, and Web of Science) and grey literature was performed. Twenty-two published studies representing 518 older adult drivers met the following inclusion criteria: the study (1) was about driving; (2) involved older drivers; (3) was qualitative (rather than quantitative or mixed methods); and (4) contained information on older drivers' perspectives about communication with health care providers. We identified 5 major themes regarding older adults' communication preferences: (1) driving discussions are emotionally charged; (2) context matters; (3) providers are trusted and viewed as authority figures; (4) communication should occur over a period of time rather than suddenly; and (5) older adults desire agency in the decision to stop driving. Various stakeholders involved in older driver safety should consider older drivers' perspectives regarding discussions about driving. Health care providers can respect and empower older drivers-and support their family members-through tactful communication about driving safety and mobility transitions during the life course.

Method of driving liquid flow at or near the free surface using magnetic microparticles

DOEpatents

Snezhko, Oleksiy [Woodridge, IL; Aronson, Igor [Darien, IL; Kwok, Wai-Kwong [Evanston, IL; Belkin, Maxim V [Woodridge, IL

2011-10-11

The present invention provides a method of driving liquid flow at or near a free surface using self-assembled structures composed of magnetic particles subjected to an external AC magnetic field. A plurality of magnetic particles are supported at or near a free surface of liquid by surface tension or buoyancy force. An AC magnetic field traverses the free surface and dipole-dipole interaction between particles produces in self-assembled snake structures which oscillate at the frequency of the traverse AC magnetic field. The snake structures independently move across the free surface and may merge with other snake structures or break up and coalesce into additional snake structures experiencing independent movement across the liquid surface. During this process, the snake structures produce asymmetric flow vortices across substantially the entirety of the free surface, effectuating liquid flow across the free surface.

Microencapsulation of curcumin in PLGA microcapsules by coaxial flow focusing

NASA Astrophysics Data System (ADS)

Lei, Fan; Si, Ting; Luo, Xisheng; Xu, Ronald X.

2014-03-01

Curcumin-loaded PLGA microcapsules are fabricated by a liquid-driving coaxial flow focusing device. In the process, a stable coaxial cone-jet configuration is formed under the action of a coflowing liquid stream and the coaxial liquid jet eventually breaks up into microcapsules because of flow instability. This process can be well controlled by adjusting the flow rates of three phases including the driving PVA water solution, the outer PLGA ethyl acetate solution and the inner curcumin propylene glycol solution. Confocal and SEM imaging methods clearly indicate the core-shell structure of the resultant microcapsules. The encapsulation rate of curcumin in PLGA is measured to be more than 70%, which is much higher than the tranditional methods such as emulsion. The size distribution of resultant microcapsules under different conditions is presented and compared. An in vitro release simulation platform is further developed to verify the feasibility and reliability of the method.

Analyzing wind turbine flow interaction through vibration data

NASA Astrophysics Data System (ADS)

Castellani, Francesco; D'Elia, Gianluca; Astolfi, Davide; Mucchi, Emiliano; Giorgio, Dalpiaz; Terzi, Ludovico

2016-09-01

Wind turbines commonly undergo non-stationary flow and, not rarely, even rather extreme phenomena. In particular, rough terrains represent a challenging testing ground, because of the combination of terrain-driven flow and wakes. It is therefore crucial to assess the impact of dynamic loads on the turbines. In this work, tower and drive-train vibrations are analyzed, from a subcluster of four turbines of a wind farm sited in a very complex terrain. The main outcome of the study is that it is possible to start from the analysis of wind conditions and interpret how wakes manifest in the vibrations of the turbines, both at structural level (tower vibrations) and at the drive-train level. This wind to gear approach therefore allows to build a connection between a flow phenomenon and a mechanical phenomenon (vibrations) and can be precious to assess loads in different working conditions.

Dynamo Induced by Time-periodic Force

NASA Astrophysics Data System (ADS)

Wei, Xing

2018-03-01

To understand the dynamo driven by time-dependent flow, e.g., turbulence, we investigate numerically the dynamo induced by time-periodic force in rotating magnetohydrodynamic flow and focus on the effect of force frequency on the dynamo action. It is found that the dynamo action depends on the force frequency. When the force frequency is near resonance the force can drive dynamo, but when it is far away from resonance dynamo fails. In the frequency range near resonance to support dynamo, the force frequency at resonance induces a weak magnetic field and magnetic energy increases as the force frequency deviates from the resonant frequency. This is opposite to the intuition that a strong flow at resonance will induce a strong field. It is because magnetic field nonlinearly couples with fluid flow in the self-sustained dynamo and changes the resonance of driving force and inertial wave.

Development of Coriolis mass flowmeter with digital drive and signal processing technology.

PubMed

Hou, Qi-Li; Xu, Ke-Jun; Fang, Min; Liu, Cui; Xiong, Wen-Jun

2013-09-01

Coriolis mass flowmeter (CMF) often suffers from two-phase flowrate which may cause flowtube stalling. To solve this problem, a digital drive method and a digital signal processing method of CMF is studied and implemented in this paper. A positive-negative step signal is used to initiate the flowtube oscillation without knowing the natural frequency of the flowtube. A digital zero-crossing detection method based on Lagrange interpolation is adopted to calculate the frequency and phase difference of the sensor output signals in order to synthesize the digital drive signal. The digital drive approach is implemented by a multiplying digital to analog converter (MDAC) and a direct digital synthesizer (DDS). A digital Coriolis mass flow transmitter is developed with a digital signal processor (DSP) to control the digital drive, and realize the signal processing. Water flow calibrations and gas-liquid two-phase flowrate experiments are conducted to examine the performance of the transmitter. The experimental results show that the transmitter shortens the start-up time and can maintain the oscillation of flowtube in two-phase flowrate condition. Copyright © 2013 ISA. Published by Elsevier Ltd. All rights reserved.

Quantum design of photosynthesis for bio-inspired solar-energy conversion.

PubMed

Romero, Elisabet; Novoderezhkin, Vladimir I; van Grondelle, Rienk

2017-03-15

Photosynthesis is the natural process that converts solar photons into energy-rich products that are needed to drive the biochemistry of life. Two ultrafast processes form the basis of photosynthesis: excitation energy transfer and charge separation. Under optimal conditions, every photon that is absorbed is used by the photosynthetic organism. Fundamental quantum mechanics phenomena, including delocalization, underlie the speed, efficiency and directionality of the charge-separation process. At least four design principles are active in natural photosynthesis, and these can be applied practically to stimulate the development of bio-inspired, human-made energy conversion systems.

Compact anhydrous HCl to aqueous HCl conversion system

DOEpatents

Grossman, M.W.; Speer, R.

1993-06-01

The present invention is directed to an inexpensive and compact apparatus adapted for use with a [sup 196]Hg isotope separation process and the conversion of anhydrous HCl to aqueous HCl without the use of air flow to carry the HCl vapor into the converter system.

Energetics of eddy-mean flow interactions in the Brazil current between 20°S and 36°S

NASA Astrophysics Data System (ADS)

Magalhães, F. C.; Azevedo, J. L. L.; Oliveira, L. R.

2017-08-01

The energetics of eddy-mean flow interactions in the Brazil Current (BC) between 20°S and 36°S are investigated in 19 transects perpendicular to the 200 m isobath. Ten years (2000-2009) of output data from the Hybrid Coordinate Ocean Model (HYCOM) NCODA reanalysis, with a spatial resolution of 1/12.5° and 5 day averages, are used. The mean kinetic energy (MKE) and eddy kinetic energy (EKE) fields presented the same subsurface spatial pattern but with reduced values. The EKE increases southward, with high values along the BC path and the offshore portion of the jet. The values of the barotropic conversion term (BTC) are highest in the surface layers and decreased with depth, whereas the values of the baroclinic conversion term (BCC) and the vertical eddy heat flux (VEHF) are highest in the subsurface. Despite the vertical thickening of the BC, the highest energy conversion rates are confined to the upper 700 m of the water column. The energetic analysis showed that the current features mixed instability processes. The vertical weighted mean of the BTC and BCC presented an oscillatory pattern related to the bathymetry. The eddy field accelerates the time-mean flow upstream and downstream of bathymetric features and drains energy from the time-mean flow over the features. The BC is baroclinically unstable south of 28°S, and the highest energy conversion rates occur in Cabo de São Tomé, Cabo Frio, and the Cone do Rio Grande.

A compressible two-phase model for dispersed particle flows with application from dense to dilute regimes

DOE Office of Scientific and Technical Information (OSTI.GOV)

McGrath, Thomas P., E-mail: thomas.p.mcgrath@navy.mil; St Clair, Jeffrey G.; Department of Mechanical and Aerospace Engineering, University of Florida, 231 MAE-A, P.O. Box 116250, Gainesville, Florida 32611

2016-05-07

Multiphase flows are present in many important fields ranging from multiphase explosions to chemical processing. An important subset of multiphase flow applications involves dispersed materials, such as particles, droplets, and bubbles. This work presents an Eulerian–Eulerian model for multiphase flows containing dispersed particles surrounded by a continuous media such as air or water. Following a large body of multiphase literature, the driving force for particle acceleration is modeled as a direct function of both the continuous-phase pressure gradient and the gradient of intergranular stress existing within the particle phase. While the application of these two components of driving force ismore » well accepted in much of the literature, other models exist in which the particle-phase pressure gradient itself drives particle motion. The multiphase model treats all phases as compressible and is derived to ensure adherence to the 2nd Law of Thermodynamics. The governing equations are presented and discussed, and a characteristic analysis shows the model to be hyperbolic, with a degeneracy in the case that the intergranular stress, which is modeled as a configuration pressure, is zero. Finally, results from a two sample problems involving shock-induced particle dispersion are presented. The results agree well with experimental measurements, providing initial confidence in the proposed model.« less

Temperature-gated thermal rectifier for active heat flow control.

PubMed

Zhu, Jia; Hippalgaonkar, Kedar; Shen, Sheng; Wang, Kevin; Abate, Yohannes; Lee, Sangwook; Wu, Junqiao; Yin, Xiaobo; Majumdar, Arun; Zhang, Xiang

2014-08-13

Active heat flow control is essential for broad applications of heating, cooling, and energy conversion. Like electronic devices developed for the control of electric power, it is very desirable to develop advanced all-thermal solid-state devices that actively control heat flow without consuming other forms of energy. Here we demonstrate temperature-gated thermal rectification using vanadium dioxide beams in which the environmental temperature actively modulates asymmetric heat flow. In this three terminal device, there are two switchable states, which can be regulated by global heating. In the "Rectifier" state, we observe up to 28% thermal rectification. In the "Resistor" state, the thermal rectification is significantly suppressed (<1%). To the best of our knowledge, this is the first demonstration of solid-state active-thermal devices with a large rectification in the Rectifier state. This temperature-gated rectifier can have substantial implications ranging from autonomous thermal management of heating and cooling systems to efficient thermal energy conversion and storage.

Effects of fexofenadine and hydroxyzine on brake reaction time during car-driving with cellular phone use.

PubMed

Tashiro, Manabu; Horikawa, Etsuo; Mochizuki, Hideki; Sakurada, Yumiko; Kato, Motohisa; Inokuchi, Takatoshi; Ridout, Fran; Hindmarch, Ian; Yanai, Kazuhiko

2005-10-01

Antihistamines are a mainstay treatment for allergic rhinitis; however, many older agents cause adverse events, including sedation and central nervous system (CNS) impairment. Research has shown sedating effects of antihistamines on driving; currently, no known study has examined whether cellular phone usage while driving further compounds impairment in individuals administered antihistamines. The aim of this study was to examine this endpoint. In a randomized, double-blind, placebo-controlled, three-way crossover study, healthy volunteers received fexofenadine HCl 120 mg, hydroxyzine HCl 30 mg and placebo. Brake reaction time (BRT) was used to examine driving performance across four conditions: driving only; driving while completing simple calculations; complex calculations; and conversing on a cellular phone. Subjective sedation assessments were also conducted. Brake reaction time with and without cellular phone usage in fexofenadine-treated subjects did not differ significantly from placebo in any condition. In contrast, hydroxyzine-treated subjects were significantly more sedated and had slower BRTs, suggesting slower hazard recognition and brake application, compared with the fexofenadine and placebo groups in all conditions. Importantly, cellular phone operation was an additive factor, increasing BRTs in hydroxyzine-treated volunteers. Fexofenadine did not impair CNS function in subjects involved in a divided attention task of driving and cellular phone operation. Copyright (c) 2005 John Wiley & Sons, Ltd.

Process for preparing a chemical compound enriched in isotope content. [nitrogen 15-enriched nitric acid

DOEpatents

Michaels, E.D.

1981-02-25

A process to prepare a chemical enriched in isotope content includes: a chemical exchange reaction between a first and second compound which yields an isotopically enriched first compound and an isotopically depleted second compound; the removal of a portion of the first compound as product and the removal of a portion of the second compound as spent material; the conversion of the remainder of the first compound to the second compound for reflux at the product end of the chemical exchange reaction region; the conversion of the remainder of the second compound to the first compound for reflux at the spent material end of the chemical exchange region; and the cycling of the additional chemicals produced by one conversion reaction to the other conversion reaction, for consumption therein. One of the conversion reactions is an oxidation reaction, and the energy that it yields is used to drive the other conversion reaction, a reduction. The reduction reaction is carried out in a solid polymer electrolyte electrolytic reactor. The overall process is energy efficient and yields no waste by-products. A particular embodiment of the process in the production of nitrogen-15-enriched nitric acid.

33 CFR 207.350 - St. Croix River, Wis. and Minn.

Code of Federal Regulations, 2010 CFR

2010-07-01

..., the full natural run of water in the river shall be permitted to flow between 1 a.m. on Thursday and 4... shall have the right to sluice, drive, and float loose logs and to regulate the flow of water in the... river flow exceeds 1,600 feet per second, the reduced flow shall be not less than 1,600 feet per second...

The nature of the laning transition in two dimensions

NASA Astrophysics Data System (ADS)

Glanz, T.; Löwen, H.

2012-11-01

If a binary colloidal mixture is oppositely driven by an external field, a transition towards a laned state occurs at sufficiently large drives, where particles driven alike form elongated structures (‘lanes’) characterized by a large correlation length ξ along the drive. Here we perform extensive Brownian dynamics computer simulations on a two-dimensional equimolar binary Yukawa system driven by a constant force that acts oppositely on the two species. We systematically address finite-size effects on lane formation by exploring large systems up to 262 144 particles under various boundary conditions. It is found that the correlation length ξ along the field depends exponentially on the driving force (or Peclet number). Conversely, in a finite system, ξ reaches a fraction of the system size at a driving force which is logarithmic in the system size, implying massive finite-size corrections. For a fixed finite drive, ξ does not diverge in the thermodynamic limit. Therefore, though laning has a signature as a sharp transition in a finite system, it is a smooth crossover in the thermodynamic limit.

The effects of perception of risk and importance of answering and initiating a cellular phone call while driving.

PubMed

Nelson, Erik; Atchley, Paul; Little, Todd D

2009-05-01

Recent data suggest that laws banning cellular phone use while driving may not change use patterns, especially among young drivers with high rates of mobile phone adoption. We examined reasons younger drivers choose or do not choose to talk on a phone while driving among a sample of young drivers (n=276) with very high ownership of cellular phones (over 99%) and a very high use of cellular phones while driving (100% for those that were primary operators of an automobile). Respondents were surveyed for patterns of use, types of call, perceived risk, and motivations for use. The data were analyzed using structural equation modeling (SEM) to explore the relationships between perceived risk of the behavior, emotionality of the call, perceived importance of the call, and how often calls were initiated versus answered. The model suggests that even though people believe that talking on a cellular phone while driving is dangerous, they will tend to initiate a cellular conversation if they believe that the call is important.

Proneural transcription factor Atoh1 drives highly efficient differentiation of human pluripotent stem cells into dopaminergic neurons.

PubMed

Sagal, Jonathan; Zhan, Xiping; Xu, Jinchong; Tilghman, Jessica; Karuppagounder, Senthilkumar S; Chen, Li; Dawson, Valina L; Dawson, Ted M; Laterra, John; Ying, Mingyao

2014-08-01

Human pluripotent stem cells (PSCs) are a promising cell resource for various applications in regenerative medicine. Highly efficient approaches that differentiate human PSCs into functional lineage-specific neurons are critical for modeling neurological disorders and testing potential therapies. Proneural transcription factors are crucial drivers of neuron development and hold promise for driving highly efficient neuronal conversion in PSCs. Here, we study the functions of proneural transcription factor Atoh1 in the neuronal differentiation of PSCs. We show that Atoh1 is induced during the neuronal conversion of PSCs and that ectopic Atoh1 expression is sufficient to drive PSCs into neurons with high efficiency. Atoh1 induction, in combination with cell extrinsic factors, differentiates PSCs into functional dopaminergic (DA) neurons with >80% purity. Atoh1-induced DA neurons recapitulate key biochemical and electrophysiological features of midbrain DA neurons, the degeneration of which is responsible for clinical symptoms in Parkinson's disease (PD). Atoh1-induced DA neurons provide a reliable disease model for studying PD pathogenesis, such as neurotoxin-induced neurodegeneration in PD. Overall, our results determine the role of Atoh1 in regulating neuronal differentiation and neuron subtype specification of human PSCs. Our Atoh1-mediated differentiation approach will enable large-scale applications of PD patient-derived midbrain DA neurons in mechanistic studies and drug screening for both familial and sporadic PD. ©AlphaMed Press.

Design criteria monograph on centrifugal flow turbopumps

NASA Technical Reports Server (NTRS)

1974-01-01

Monograph reviews and assesses current design practices, and from them establishes firm guidance for achieving greater consistency in design, increased reliability in end product, and greater efficiency in design effort. Review should be of interest to manufacturers and users of pumps, power drives, turbine drives, and rotary equipment in general.

Improving the mixing performance of side channel type micromixers using an optimal voltage control model.

PubMed

Wu, Chien-Hsien; Yang, Ruey-Jen

2006-06-01

Electroosmotic flow in microchannels is restricted to low Reynolds number regimes. Since the inertia forces are extremely weak in such regimes, turbulent conditions do not readily develop, and hence species mixing occurs primarily as a result of diffusion. Consequently, achieving a thorough species mixing generally relies upon the use of extended mixing channels. This paper aims to improve the mixing performance of conventional side channel type micromixers by specifying the optimal driving voltages to be applied to each channel. In the proposed approach, the driving voltages are identified by constructing a simple theoretical scheme based on a 'flow-rate-ratio' model and Kirchhoff's law. The numerical and experimental results confirm that the optimal voltage control approach provides a better mixing performance than the use of a single driving voltage gradient.

Investigation of the Link Between Macroscopic Traffic Flow Characteristics and Individual Vehicle Fuel Consumption : Tech Transfer Summary

DOT National Transportation Integrated Search

2017-10-01

The objective of this project was to investigate the impacts of several factors, including vehicle characteristics, ambient temperature, season, speed, driving behavior, and traffic flow, on individual vehicle energy consumption.

Investigation of the Link Between Macroscopic Traffic Flow Characteristics and Individual Vehicle Fuel Consumption

DOT National Transportation Integrated Search

2017-10-01

This project investigated the factors impacting individual vehicle energy consumption, including vehicle characteristics, ambient temperature, season, speed, driving behavior, and traffic flow. A fleet of 18 vehicles with a variety of ownership, size...

Rotation motion of designed nano-turbine.

PubMed

Li, Jingyuan; Wang, Xiaofeng; Zhao, Lina; Gao, Xingfa; Zhao, Yuliang; Zhou, Ruhong

2014-07-28

Construction of nano-devices that can generate controllable unidirectional rotation is an important part of nanotechnology. Here, we design a nano-turbine composed of carbon nanotube and graphene nanoblades, which can be driven by fluid flow. Rotation motion of nano-turbine is quantitatively studied by molecular dynamics simulations on this model system. A robust linear relationship is achieved with this nano-turbine between its rotation rate and the fluid flow velocity spanning two orders of magnitude, and this linear relationship remains intact at various temperatures. More interestingly, a striking difference from its macroscopic counterpart is identified: the rotation rate is much smaller (by a factor of ~15) than that of the macroscopic turbine with the same driving flow. This discrepancy is shown to be related to the disruption of water flow at nanoscale, together with the water slippage at graphene surface and the so-called "dragging effect". Moreover, counterintuitively, the ratio of "effective" driving flow velocity increases as the flow velocity increases, suggesting that the linear dependence on the flow velocity can be more complicated in nature. These findings may serve as a foundation for the further development of rotary nano-devices and should also be helpful for a better understanding of the biological molecular motors.

Hemodynamics

PubMed Central

Secomb, Timothy W.

2016-01-01

A review is presented of the physical principles governing the distribution of blood flow and blood pressure in the vascular system. The main factors involved are the pulsatile driving pressure generated by the heart, the flow characteristics of blood, and the geometric structure and mechanical properties of the vessels. The relationship between driving pressure and flow in a given vessel can be understood by considering the viscous and inertial forces acting on the blood. Depending on the vessel diameter and other physical parameters, a wide variety of flow phenomena can occur. In large arteries, the propagation of the pressure pulse depends on the elastic properties of the artery walls. In the microcirculation, the fact that blood is a suspension of cells strongly influences its flow properties and leads to a non-uniform distribution of hematocrit among microvessels. The forces acting on vessel walls include shear stress resulting from blood flow and circumferential stress resulting from blood pressure. Biological responses to these forces are important in the control of blood flow and the structural remodeling of vessels, and also play a role in major disease processes including hypertension and atherosclerosis. Consideration of hemodynamics is essential for a comprehensive understanding of the functioning of the circulatory system. PMID:27065172

Synthesis of Biodiesel in Batch and Packed-Bed Reactors Using Powdered and Granular Sugar Catalyst

NASA Astrophysics Data System (ADS)

Janaun, J.; Lim, P. M.; Balan, W. S.; Yaser, A. Z.; Chong, K. P.

2017-06-01

Increasing world production of palm oil warrants effective utilization of its waste. In particular, conversion of waste cooking oil into biodiesel has obtained global interest because of renewable energy need and reduction of CO2 emission. In this study, oleic acid used as a model compound for waste cooking oil conversion using esterification reaction catalysed by sugar catalyst (SC) in powdered (P-SC) and granular (G-SC) forms. The catalysts were synthesized via incomplete carbonization of D-glucose followed by functionalization with concentrated sulphuric acid. Catalysts characterizations were done for their physical and chemical properties using modern tools. Batch and packed-bed reactor systems were used to evaluate the reactivity of the catalysts. The results showed that G-SC had slightly higher total acidity and more porous than P-SC. The experimental conditions for batch reaction were temperature of 60°C, molar ratio of 1:20 (Oleic Acid:Methanol) and 2 wt. catalyst with respect to oleic acid. The results showed the maximum oleic acid conversion using G-SC and P-SC were 52 and 48, respectively. Whereas, the continuous reaction with varying feed flow rate as a function of retention time was studied by using 3 g of P-SC in 60 °C and 1:20 molar ratio in a packed-bed reactor. The results showed that a longer retention time which was 6.48 min and feed flow rate 1.38 ml/min, achieved higher average conversion of 9.9 and decreased with further increasing flow rate. G-SC showed a better average conversion of 10.8 at lowest feed flow rate of 1.38 ml/min in continuous reaction experiments. In a broader perspective, large scale continuous biodiesel production is feasible using granular over powdered catalyst mainly due to it lower pressure drop.

Cooling by Para-to-Ortho-Hydrogen Conversion

NASA Technical Reports Server (NTRS)

Sherman, A.; Nast, T.

1983-01-01

Catalyst speeds conversion, increasing capacity of solid hydrogen cooling system. In radial-flow catalytic converter, para-hydrogen is converted to equilibrium mixture of para-hydrogen and ortho-hydrogen as it passes through porous cylinder of catalyst. Addition of catalyst increases capacity of hydrogen sublimation cooling systems for radiation detectors.

1995 NPTS user's guide for the public use data files : nationwide personal transportation survey

DOT National Transportation Integrated Search

2000-04-01

Given the lack of funds for new highway construction and the ever-increasing traffic flows, the issue of conversion from two lanes to four lanes is of increasing importance. The best way to assess the safety effects of these conversions would be to d...

Energy efficient engine: Preliminary design and integration studies

NASA Technical Reports Server (NTRS)

Johnston, R. P.; Hirschkron, R.; Koch, C. C.; Neitzel, R. E.; Vinson, P. W.

1978-01-01

Parametric design and mission evaluations of advanced turbofan configurations were conducted for future transport aircraft application. Economics, environmental suitability and fuel efficiency were investigated and compared with goals set by NASA. Of the candidate engines which included mixed- and separate-flow, direct-drive and geared configurations, an advanced mixed-flow direct-drive configuration was selected for further design and evaluation. All goals were judged to have been met except the acoustic goal. Also conducted was a performance risk analysis and a preliminary aerodynamic design of the 10 stage 23:1 pressure ratio compressor used in the study engines.

New mechanism to reduce the size of the monopivot magnetic suspension blood pump: direct drive mechanism.

PubMed

Yamane, T; Nishida, M; Kijima, T; Maekawa, J

1997-07-01

Size reduction of the monopivot magnetic suspension blood pump has been achieved by reducing the size of the magnetic suspension and employing a direct drive mechanism in place of a brushless DC motor and a magnetic coupling. The flow has also been improved using a closed hollow impeller to remove flow obstruction at the inlet and using radial straight vanes to reduce the impeller speed by 30%. Hemolysis testing was conducted for the new models. Results showed that model DD1 presented only a slightly higher level of hemolysis than a regular extracorporeal centrifugal pump.

Bulk Viscosity of Bubbly Magmas and the Amplification of Pressure Waves

NASA Astrophysics Data System (ADS)

Navon, O.; Lensky, N. G.; Neuberg, J. W.; Lyakhovsky, V.

2001-12-01

The bulk viscosity of magma is needed in order to describe the dynamics of a compressible bubbly magma flowing in conduits and to follow the attenuation of pressure waves travelling through a compressible magma. We developed a model for the bulk viscosity of a suspension of gas bubbles in an incompressible Newtonian liquid that exsolves volatiles (e.g. magma). The suspension is modeled as a close pack of spherical cells, consisting of gas bubbles centered in spherical shells of a volatile-bearing liquid. Following a drop in the ambient pressure the resulting dilatational motion and driving pressure are obtained in terms of the two-phase cell parameters, i.e. bubble radius and gas pressure. By definition, the bulk viscosity of a fluid is the relation between changes of the driving pressure with respect to changes in the resulted expansion strain-rate. Thus, we can use the two-phase solution to define the bulk viscosity of a hypothetical cell, composed of a homogeneously compressible, one-phase, continuous fluid. The resulted bulk viscosity is highly non-linear. At the beginning of the expansion process, when gas exsolution is efficient, the expansion rate grows exponentially while the driving pressure decreases slightly. That means that bulk viscosity is formally negative. The negative value reflects the release of the energy stored in the supersaturated liquid (melt) and its conversion to mechanical work during exsolution. Later, when bubbles are large enough and the gas influx decreases significantly, the strain rate decelerates and the bulk viscosity becomes positive as expected in a dissipative system. We demonstrate that amplification of seismic wave travelling through a volcanic conduit filled with a volatile saturated magma may be attributed to the negative bulk viscosity of the compressible magma. Amplification of an expansion wave may, at some level in the conduit, damage the conduit walls and initiate opening of new pathways for magma to erupt.

Design of Interactively Time-Pulsed Microfluidic Mixers in Microchips using Numerical Simulation

NASA Astrophysics Data System (ADS)

Fu, Lung-Ming; Tsai, Chien-Hsiung

2007-01-01

In this paper, we propose a novel technique in which driving voltages are applied interactively to the respective inlet fluid flows of three configurations of a microfluidic device, namely T-shaped, double-T-shaped, and double-cross-shaped configurations, to induce electroosmotic flow (EOF) velocity variations in such a way as to develop a rapid mixing effect in the microchannel. In these configurations a microfluidic mixer apply only one electrokinetic driving force, which drives the sample fluids and simultaneously produces a periodic switching frequency. It requires no other external driving force to induce perturbations to the flow field. The effects of the main applied electric field, the interactive frequency, and the pullback electric field on the mixing performance are thoroughly examined numerically. The optimal interactive frequency range for a given set of micromixer parameters is identified for each type of control mode. The numerical results confirm that micromixers operating at an optimal interactive frequency are capable of delivering a significantly enhanced mixing performance. Furthermore, it is shown that the optimal interactive frequency depends upon the magnitude of the main applied electric field. The interactively pulsed mixers developed in this study have a strong potential for use in lab-on-a-chip systems. They involve a simpler fabrication process than either passive or active on-chip mixers and require less human intervention in operation than their bulky external counterparts.

Self-Organization in 2D Traffic Flow Model with Jam-Avoiding Drive

NASA Astrophysics Data System (ADS)

Nagatani, Takashi

1995-04-01

A stochastic cellular automaton (CA) model is presented to investigate the traffic jam by self-organization in the two-dimensional (2D) traffic flow. The CA model is the extended version of the 2D asymmetric exclusion model to take into account jam-avoiding drive. Each site contains either a car moving to the up, a car moving to the right, or is empty. A up car can shift right with probability p ja if it is blocked ahead by other cars. It is shown that the three phases (the low-density phase, the intermediate-density phase and the high-density phase) appear in the traffic flow. The intermediate-density phase is characterized by the right moving of up cars. The jamming transition to the high-density jamming phase occurs with higher density of cars than that without jam-avoiding drive. The jamming transition point p 2c increases with the shifting probability p ja. In the deterministic limit of p ja=1, it is found that a new jamming transition occurs from the low-density synchronized-shifting phase to the high-density moving phase with increasing density of cars. In the synchronized-shifting phase, all up cars do not move to the up but shift to the right by synchronizing with the move of right cars. We show that the jam-avoiding drive has an important effect on the dynamical jamming transition.

Myocardial perfusion cardiovascular magnetic resonance: optimized dual sequence and reconstruction for quantification.

PubMed

Kellman, Peter; Hansen, Michael S; Nielles-Vallespin, Sonia; Nickander, Jannike; Themudo, Raquel; Ugander, Martin; Xue, Hui

2017-04-07

Quantification of myocardial blood flow requires knowledge of the amount of contrast agent in the myocardial tissue and the arterial input function (AIF) driving the delivery of this contrast agent. Accurate quantification is challenged by the lack of linearity between the measured signal and contrast agent concentration. This work characterizes sources of non-linearity and presents a systematic approach to accurate measurements of contrast agent concentration in both blood and myocardium. A dual sequence approach with separate pulse sequences for AIF and myocardial tissue allowed separate optimization of parameters for blood and myocardium. A systems approach to the overall design was taken to achieve linearity between signal and contrast agent concentration. Conversion of signal intensity values to contrast agent concentration was achieved through a combination of surface coil sensitivity correction, Bloch simulation based look-up table correction, and in the case of the AIF measurement, correction of T2* losses. Validation of signal correction was performed in phantoms, and values for peak AIF concentration and myocardial flow are provided for 29 normal subjects for rest and adenosine stress. For phantoms, the measured fits were within 5% for both AIF and myocardium. In healthy volunteers the peak [Gd] was 3.5 ± 1.2 for stress and 4.4 ± 1.2 mmol/L for rest. The T2* in the left ventricle blood pool at peak AIF was approximately 10 ms. The peak-to-valley ratio was 5.6 for the raw signal intensities without correction, and was 8.3 for the look-up-table (LUT) corrected AIF which represents approximately 48% correction. Without T2* correction the myocardial blood flow estimates are overestimated by approximately 10%. The signal-to-noise ratio of the myocardial signal at peak enhancement (1.5 T) was 17.7 ± 6.6 at stress and the peak [Gd] was 0.49 ± 0.15 mmol/L. The estimated perfusion flow was 3.9 ± 0.38 and 1.03 ± 0.19 ml/min/g using the BTEX model and 3.4 ± 0.39 and 0.95 ± 0.16 using a Fermi model, for stress and rest, respectively. A dual sequence for myocardial perfusion cardiovascular magnetic resonance and AIF measurement has been optimized for quantification of myocardial blood flow. A validation in phantoms was performed to confirm that the signal conversion to gadolinium concentration was linear. The proposed sequence was integrated with a fully automatic in-line solution for pixel-wise mapping of myocardial blood flow and evaluated in adenosine stress and rest studies on N = 29 normal healthy subjects. Reliable perfusion mapping was demonstrated and produced estimates with low variability.

Microstreaming from Sessile Semicylindrical Bubbles

NASA Astrophysics Data System (ADS)

Hilgenfeldt, Sascha; Rallabandi, Bhargav; Guo, Lin; Wang, Cheng

2014-03-01

Powerful steady streaming flows result from the ultrasonic driving of microbubbles, in particular when these bubbles have semicylindrical cross section and are positioned in contact with a microfluidic channel wall. We have used this streaming in experiment to develop novel methods for trapping and sorting of microparticles by size, as well as for micromixing. Theoretically, we arrive at an analytical description of the streaming flow field through an asymptotic computation that, for the first time, reconciles the boundary layers around the bubble and along the substrate wall, and also takes into account the oscillation modes of the bubble. This approach gives insight into changes in the streaming pattern with bubble size and driving frequency, including a reversal of the flow direction at high frequencies with potentially useful applications. Present address: Mechanical and Aerospace Engineering, Missouri S &T.

Modeling the effect of microscopic driving behaviors on Kerner's time-delayed traffic breakdown at traffic signal using cellular automata

NASA Astrophysics Data System (ADS)

Wang, Yang; Chen, Yan-Yan

2016-12-01

The signalized traffic is considerably complex due to the fact that various driving behaviors have emerged to respond to traffic signals. However, the existing cellular automaton models take the signal-vehicle interactions into account inadequately, resulting in a potential risk that vehicular traffic flow dynamics may not be completely explored. To remedy this defect, this paper proposes a more realistic cellular automaton model by incorporating a number of the driving behaviors typically observed when the vehicles are approaching a traffic light. In particular, the anticipatory behavior proposed in this paper is realized with a perception factor designed by considering the vehicle speed implicitly and the gap to its preceding vehicle explicitly. Numerical simulations have been performed based on a signal controlled road which is partitioned into three sections according to the different reactions of drivers. The effects of microscopic driving behaviors on Kerner's time-delayed traffic breakdown at signal (Kerner 2011, 2013) have been investigated with the assistance of spatiotemporal pattern and trajectory analysis. Furthermore, the contributions of the driving behaviors on the traffic breakdown have been statistically examined. Finally, with the activation of the anticipatory behavior, the influences of the other driving behaviors on the formation of platoon have been investigated in terms of the number of platoons, the averaged platoon size, and the averaged flow rate.

Non-isothermal crystallization of poly(etheretherketone) aromatic polymer composite

NASA Technical Reports Server (NTRS)

Cebe, Peggy

1988-01-01

The nonisothermal crystallization kinetics of PEEK APC-2 and of 450G neat resin PEEK material were compared using a differential scanning calorimeter to monitor heat flow during crystallization; the effects of cooling rate on the crystallization temperature, the degree of crystallinity, and the conversion rate were investigated. A modified Avrami (1940) analysis was used to describe nonisothermal crystallization kinetics. It was found that, compared with the 450G neat resin PEEK, the nonisothermal crystallization of the PEEK APC-2 composite is characterized by higher initiation temperature, higher heat flow maximum temperature, and greater relative conversion by primary processes.

Marine Propulsion Load Emulation.

DTIC Science & Technology

1985-06-01

single-entry centrifugal compressor mechanically coupled to a single-stage axial - flow turbine , two cross- connected can type combustion chambers, and...an accessory- drive section. The power output section incorporates a second axial - flow turbine , reduction gears and output shaft, and is driven by the... Flow .... ............. ... 36 4.7 Load Valve Characteristics ... ............. .38 4.8 Photograph of Turbine Test gell .......... 39, * 4.9

[Ecological management model of agriculture-pasture ecotone based on the theory of energy and material flow--a case study in Houshan dryland area of Inner Mongolia].

PubMed

Fan, Jinlong; Pan, Zhihua; Zhao, Ju; Zheng, Dawei; Tuo, Debao; Zhao, Peiyi

2004-04-01

The degradation of ecological environment in the agriculture-pasture ecotone in northern China has been paid more attentions. Based on our many years' research and under the guide of energy and material flow theory, this paper put forward an ecological management model, with a hill as the basic cell and according to the natural, social and economic characters of Houshan dryland farming area inside the north agriculture-pasture ecotone. The input and output of three models, i.e., the traditional along-slope-tillage model, the artificial grassland model and the ecological management model, were observed and recorded in detail in 1999. Energy and material flow analysis based on field test showed that compared with traditional model, ecological management model could increase solar use efficiency by 8.3%, energy output by 8.7%, energy conversion efficiency by 19.4%, N output by 26.5%, N conversion efficiency by 57.1%, P output by 12.1%, P conversion efficiency by 45.0%, and water use efficiency by 17.7%. Among the models, artificial grassland model had the lowest solar use efficiency, energy output and energy conversion efficiency; while the ecological management model had the most outputs and benefits, was the best model with high economic effect, and increased economic benefits by 16.1%, compared with the traditional model.

Analysis of key factors influencing the evaporation performances of an oriented linear cutting copper fiber sintered felt

NASA Astrophysics Data System (ADS)

Pan, Minqiang; Zhong, Yujian

2018-01-01

Porous structure can effectively enhance the heat transfer efficiency. A kind of micro vaporizer using the oriented linear cutting copper fiber sintered felt is proposed in this work. Multiple long cutting copper fibers are firstly fabricated with a multi-tooth tool and then sintered together in parallel to form uniform thickness metal fiber sintered felts that provided a characteristic of oriented microchannels. The temperature rise response and thermal conversion efficiency are experimentally investigated to evaluate the influences of porosity, surface structure, feed flow rate and input power on the evaporation characteristics. It is indicated that the temperature rise response of water is mainly affected by input power and feed flow rate. High input power and low feed flow rate present better temperature rise response of water. Porosity rather than surface structure plays an important role in the temperature rise response of water at a relatively high input power. The thermal conversion efficiency is dominated by the input power and surface structure. The oriented linear cutting copper fiber sintered felts for three kinds of porosities show better thermal conversion efficiency than that of the oriented linear copper wire sintered felt when the input power is less than 115 W. All the sintered felts have almost the same performance of thermal conversion at a high input power.

Topological Frequency Conversion in Strongly Driven Quantum Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martin, Ivar; Refael, Gil; Halperin, Bertrand

When a physical system is subjected to a strong external multi-frequency drive, its dynamics can be conveniently represented in the multi-dimensional Floquet lattice. The number of the Floquet lattice dimensions equals the number of irrationally-related drive frequencies, and the evolution occurs in response to a built-in effective \\electric" field, whose components are proportional to the corresponding drive frequencies. The mapping allows to engineer and study temporal analogs of many real-space phenomena. Here we focus on the specifc example of a two-level system under two-frequency drive that induces topologically nontrivial band structure in the 2D Floquet space. The observable consequence ofmore » such construction is quantized pumping of energy between the sources with frequencies w 1 and w 2. Finally, when the system is initialized into a Floquet band with the Chern number C, the pumping occurs at the rate P 12 = – P 21 = ( C/2π)hw 1w 2, an exact counterpart of the transverse current in a conventional topological insulator.« less

Topological Frequency Conversion in Strongly Driven Quantum Systems

DOE PAGES

Martin, Ivar; Refael, Gil; Halperin, Bertrand

2017-10-16

When a physical system is subjected to a strong external multi-frequency drive, its dynamics can be conveniently represented in the multi-dimensional Floquet lattice. The number of the Floquet lattice dimensions equals the number of irrationally-related drive frequencies, and the evolution occurs in response to a built-in effective \\electric" field, whose components are proportional to the corresponding drive frequencies. The mapping allows to engineer and study temporal analogs of many real-space phenomena. Here we focus on the specifc example of a two-level system under two-frequency drive that induces topologically nontrivial band structure in the 2D Floquet space. The observable consequence ofmore » such construction is quantized pumping of energy between the sources with frequencies w 1 and w 2. Finally, when the system is initialized into a Floquet band with the Chern number C, the pumping occurs at the rate P 12 = – P 21 = ( C/2π)hw 1w 2, an exact counterpart of the transverse current in a conventional topological insulator.« less

Self-Driving Cars and Engineering Ethics: The Need for a System Level Analysis.

PubMed

Borenstein, Jason; Herkert, Joseph R; Miller, Keith W

2017-11-13

The literature on self-driving cars and ethics continues to grow. Yet much of it focuses on ethical complexities emerging from an individual vehicle. That is an important but insufficient step towards determining how the technology will impact human lives and society more generally. What must complement ongoing discussions is a broader, system level of analysis that engages with the interactions and effects that these cars will have on one another and on the socio-technical systems in which they are embedded. To bring the conversation of self-driving cars to the system level, we make use of two traffic scenarios which highlight some of the complexities that designers, policymakers, and others should consider related to the technology. We then describe three approaches that could be used to address such complexities and their associated shortcomings. We conclude by bringing attention to the "Moral Responsibility for Computing Artifacts: The Rules", a framework that can provide insight into how to approach ethical issues related to self-driving cars.

Acoustic Emission Characteristics of Nanocrystalline Porous Silicon Device Driven as an Ultrasonic Speaker

NASA Astrophysics Data System (ADS)

Tsubaki, Kenji; Komoda, Takuya; Koshida, Nobuyoshi

2006-04-01

It is shown that the dc-superimposed driving mode is more useful for the efficient operation of a novel thermally induced ultrasonic emitter based on nanocrystalline porous silicon (nc-PS) than the conventional simple ac-voltage driving mode. The nc-PS device is composed of a patterned heater electrode, an nc-PS layer and a single crystalline silicon (c-Si) substrate. The almost complete thermally insulating property of nc-PS as a quantum-sized system makes it possible to apply the nc-PS device as an ultrasonic generator by efficient thermo acoustic conversion without any mechanical vibrations. In the dc-superimposed driving mode, the output frequency is the same as the input frequency and a stationary temperature rise is kept constant independent of input peak-to-peak voltage. In addition, power efficiency is significantly increases compared with that in the ac-voltage driving mode without affecting on the temperature rise. The present results suggest the further possibility of the nc-PS device being used as a functional speaker.

Evidence of sublaminar drag naturally occurring in a curved pipe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noorani, A.; Schlatter, P., E-mail: pschlatt@mech.kth.se

Steady and unsteady flows in a mildly curved pipe for a wide range of Reynolds numbers are examined with direct numerical simulation. It is shown that in a range of Reynolds numbers in the vicinity of Re{sub b} ≈ 3400, based on bulk velocity and pipe diameter, a marginally turbulent flow is established in which the friction drag naturally reduces below the laminar solution at the same Reynolds number. The obtained values for friction drag for the laminar and turbulent (sublaminar) flows turn out to be in excellent agreement with experimental measurements in the literature. Our results are also inmore » agreement with Fukagata et al. [“On the lower bound of net driving power in controlled duct flows,” Phys. D 238, 1082 (2009)], as the lower bound of net power required to drive the flow, i.e., the pressure drop of the Stokes solution, is still lower than our marginally turbulent flow. A large-scale traveling structure that is thought to be responsible for that behaviour is identified in the instantaneous field. This mode could also be extracted using proper orthogonal decomposition. The effect of this mode is to redistribute the mean flow in the circular cross section which leads to lower gradients at the wall compared to the laminar flow.« less

Evidence of sublaminar drag naturally occurring in a curved pipe

NASA Astrophysics Data System (ADS)

Noorani, A.; Schlatter, P.

2015-03-01

Steady and unsteady flows in a mildly curved pipe for a wide range of Reynolds numbers are examined with direct numerical simulation. It is shown that in a range of Reynolds numbers in the vicinity of Reb ≈ 3400, based on bulk velocity and pipe diameter, a marginally turbulent flow is established in which the friction drag naturally reduces below the laminar solution at the same Reynolds number. The obtained values for friction drag for the laminar and turbulent (sublaminar) flows turn out to be in excellent agreement with experimental measurements in the literature. Our results are also in agreement with Fukagata et al. ["On the lower bound of net driving power in controlled duct flows," Phys. D 238, 1082 (2009)], as the lower bound of net power required to drive the flow, i.e., the pressure drop of the Stokes solution, is still lower than our marginally turbulent flow. A large-scale traveling structure that is thought to be responsible for that behaviour is identified in the instantaneous field. This mode could also be extracted using proper orthogonal decomposition. The effect of this mode is to redistribute the mean flow in the circular cross section which leads to lower gradients at the wall compared to the laminar flow.

The Debye-Huckel Approximation in Electroosmotic Flow in Micro- and Nano-channels

NASA Astrophysics Data System (ADS)

Conlisk, A. Terrence

2002-11-01

In this work we consider the electroosmotic flow in a rectangular channel. We consider a mixture of water or other neutral solvent and a salt compound such as sodium chloride and other buffers for which the ionic species are entirely dissociated. Results are produced for the case where the channel height is much greater than the electric double layer(EDL)(microchannel) and for the case where the channel height is of the order or slightly greater than the width of the EDL(nanochannel). At small cation, anion concentration differences the Debye-Huckel approximation is appropriate; at larger concentration differences, the Gouy-Chapman picture of the electric double emerges naturally. In the symmetric case for the electroosmotic flow so induced, the velocity field and the potential are similar. We specifically focus in this paper on the limits of the Debye-Huckel approximation for a simplified version of a phosphate buffered saline(PBS) mixture. The fluid is assumed to behave as a continuum and the volume flow rate is observed to vary linearly with channel height for electrically driven flow in contrast to pressure driven flow which varies as height cubed. This means that very large pressure drops are required to drive flows in small channels. However, useful volume flow rates may be obtained at a very low driving voltage.

Forest restoration in a global context

Treesearch

John A. Stanturf

2000-01-01

Forest restoration on land cleared for agriculture is occurring around the world. Often land was abandoned because of infertility, frequent flooding, or other site limitations. In some countries, market forces or changing trade policies drive conversion of cleared land to plantations of exotic or native tree species. The objective of this paper is to introduce the...

Creating a Campus Community for Conversation about Assessing Student Learning

ERIC Educational Resources Information Center

Musun, Linda; Baker, Aaron D.; Fulmer, Jim

2006-01-01

While assessment of student learning outcomes has become standard operating procedure on virtually every campus, the driving forces for pursuing assessment remain primarily external. For that to change, campuses must evolve toward a culture of assessment based on the shared values and expectations that arise out of a community. The first step in…

Effects of Classroom Cell Phone Use on Expected and Actual Learning

ERIC Educational Resources Information Center

Froese, Arnold D.; Carpenter, Christina N.; Inman, Denyse A.; Schooley, Jessica R.; Barnes, Rebecca B.; Brecht, Paul W.; Chacon, Jasmin D.

2012-01-01

Studies of driving indicate that the conversational aspects of using cell phones generate high risks from divided attention. Prior surveys document high rates at which students carry phones to and use them during class. Some experiments have demonstrated that cell phones distract students from learning. The present studies combined survey and…

Hybrid drive for motor vehicles with a preponderantly intermittent method of operation

NASA Technical Reports Server (NTRS)

Schreck, H.

1977-01-01

A flywheel hybrid propulsion system is compared with a conventional propulsion system in a test vehicle under intermittent operation. An energy balance is presented for the conventional propulsion system. Results so far indicate especially high energy conversion of the gyro component under dynamic operation along with favorable internal combustion engine conditions.

Driving Change in Detroit: Libraries Innovating in Step with the Community

ERIC Educational Resources Information Center

Meyer, Jessica; Chang, Allister; Trujillo, Kat

2017-01-01

Often, the conversation about Detroit features the same words used over and over again: poor, broken, abandoned, blighted. But the authors' experiences in the Motor City have shown them something completely different--a community that, in the face of overwhelming challenges, maintains a profound commitment to making Detroit a better place. This…

Microwave plasma generation of hydrogen atoms for rocket propulsion

NASA Technical Reports Server (NTRS)

Chapman, R.; Filpus, J.; Morin, T.; Snellenberger, R.; Asmussen, J.; Hawley, M.; Kerber, R.

1981-01-01

A flow microwave plasma reaction system is used to study the conversion of hydrogen to hydrogen atoms as a function of pressure, power density, cavity tuning, cavity mode, and time in the plasma zone. Hydrogen atom concentration is measured down-stream from the plasma by NOCl titration. Extensive modeling of the plasma and recombination zones is performed with the plasma zone treated as a backmix reaction system and the recombination zone treated as a plug flow. The thermodynamics and kinetics of the recombination process are examined in detail to provide an understanding of the conversion of recombination energy to gas kinetic energy. It is found that cavity tuning, discharge stability, and optimum power coupling are critically dependent on the system pressure, but nearly independent of the flow rate.

Particle-in-cell Simulation of Dipolarization Front Associated Whistlers

NASA Astrophysics Data System (ADS)

Lin, D.; Scales, W.; Ganguli, G.; Crabtree, C. E.

2017-12-01

Dipolarization fronts (DFs) are dipolarized magnetic field embedded in the Earthward propagating bursty bulk flows (BBFs), which separates the hot, tenuous high-speed flow from the cold, dense, and slowly convecting surrounding plasma [Runov et al. 2011]. Broadband fluctuations have been observed at DFs including the electromagnetic whistler waves and electrostatic lower hybrid waves in the Very Low Frequency (VLF) range [e.g., Zhou et al. 2009, Deng et al. 2010]. There waves are suggested to be able heat electrons and play a critical role in the plasma sheet dynamics [Chaston et al., 2012, Angelopoulos et al., 2013]. However, their generation mechanism and role in the energy conversion are still under debate. The gradient scale of magnetic field, plasma density at DFs in the near-Earth magnetotail is comparable to or lower than the ion gyro radius [Runov et al., 2011, Fu et al., 2012, Breuillard et al., 2016]. Such strongly inhomogeneous configuration could be unstable to the electron-ion hybrid (EIH) instability, which arises from strongly sheared transverse flow and is in the VLF range [Ganguli et al. 1988, Ganguli et al. 2014]. The equilibrium of the EIH theory implies an anisotropy of electron temperature, which are likely to drive the whistler waves observed in DFs [Deng et al., 2010, Gary et al., 2011]. In order to better understand how the whistler waves are generated in DFs and whether the EIH theory is applicable, a fully electromagnetic particle-in-cell (EMPIC) model is used to simulate the EIH instability with similar equilibrium configurations in DF observations. The EMPIC model deals with three dimensions in the velocity space and two dimensions in the configuration space, which is quite ready to include the third configuration dimension. Simulation results will be shown in this presentation.

Solar-Powered Plasmon-Enhanced Heterogeneous Catalysis

NASA Astrophysics Data System (ADS)

Naldoni, Alberto; Riboni, Francesca; Guler, Urcan; Boltasseva, Alexandra; Shalaev, Vladimir M.; Kildishev, Alexander V.

2016-06-01

Photocatalysis uses semiconductors to convert sunlight into chemical energy. Recent reports have shown that plasmonic nanostructures can be used to extend semiconductor light absorption or to drive direct photocatalysis with visible light at their surface. In this review, we discuss the fundamental decay pathway of localized surface plasmons in the context of driving solar-powered chemical reactions. We also review different nanophotonic approaches demonstrated for increasing solar-to-hydrogen conversion in photoelectrochemical water splitting, including experimental observations of enhanced reaction selectivity for reactions occurring at the metalsemiconductor interface. The enhanced reaction selectivity is highly dependent on the morphology, electronic properties, and spatial arrangement of composite nanostructures and their elements. In addition, we report on the particular features of photocatalytic reactions evolving at plasmonic metal surfaces and discuss the possibility of manipulating the reaction selectivity through the activation of targeted molecular bonds. Finally, using solar-to-hydrogen conversion techniques as an example, we quantify the efficacy metrics achievable in plasmon-driven photoelectrochemical systems and highlight some of the new directions that could lead to the practical implementation of solar-powered plasmon-based catalytic devices.

Nonlinear Photochromic Switching in the Plasmonic Field of a Nanoparticle Array

NASA Astrophysics Data System (ADS)

Otolski, Christopher J.; Argyropoulos, Christos; Elles, Christopher G.

2017-06-01

Plasmonic nanostructures provide unique environments for non-resonant excitation and switching of photochromic compounds. In this study, photochromic diarylethene molecules were deposited on top of a periodically ordered array of gold nanorods (170 x 80 nm) and then irradiated with <100 fs laser pulses. Irradiation at 800 nm drives the plasmon resonance of the nanoparticle array and induces the photochromic conversion of molecules via non-resonant two-photon excitation. Transmission measurements using broadband continuum laser pulses probe the progress of the photochemical cycloreversion reaction as molecules switch from a visible-absorbing closed-ring structure to a transparent open-ring structure. The spatial dependence of the two-photon conversion of molecules in the plasmonic near field of the array is modeled using calculated field enhancements, and compared with similar measurements for a film of molecules on a glass substrate. Wavelength-dependent polarization effects in the near field of the array lead to interesting anisotropy results in the transmission signal. The results emphasize the importance of both the spatial dependence and anisotropy of the enhanced electric fields in driving non-resonant photochromic reactions.

A novel ZVS high voltage power supply for micro-channel plate photomultiplier tubes

NASA Astrophysics Data System (ADS)

Pei, Chengquan; Tian, Jinshou; Liu, Zhen; Qin, Hong; Wu, Shengli

2017-04-01

A novel resonant high voltage power supply (HVPS) with zero voltage switching (ZVS), to reduce the voltage stress on switching devices and improve conversion efficiency, is proposed. The proposed HVPS includes a drive circuit, a transformer, several voltage multiplying circuits, and a regulator circuit. The HVPS contains several secondary windings that can be precisely regulated. The proposed HVPS performed better than the traditional resistor voltage divider, which requires replacing matching resistors resulting in resistor dispersibility in the Micro-Channel Plate (MCP). The equivalent circuit of the proposed HVPS was established and the operational principle analyzed. The entire switching element can achieve ZVS, which was validated by a simulation and experiments. The properties of this HVPS were tested including minimum power loss (240 mW), maximum power loss (1 W) and conversion efficiency (85%). The results of this research are that the proposed HVPS was suitable for driving the micro-channel plate photomultiplier tube (MCP-PMT). It was therefore adopted to test the MCP-PMT, which will be used in Daya Bay reactor neutrino experiment II in China.

[Effects of white organic light-emitting devices using color conversion films on electroluminescence spectra].

PubMed

Hou, Qing-Chuan; Wu, Xiao-Ming; Hua, Yu-Lin; Qi, Qing-Jin; Li, Lan; Yin, Shou-Gen

2010-06-01

The authors report a novel white organic light-emitting device (WOLED), which uses a strategy of exciting organic/ inorganic color conversion film with a blue organic light-emitting diode (OLED). The luminescent layer of the blue OLED was prepared by use of CBP host blended with a blue highly fluorescent dye N-BDAVBi. The organic/inorganic color conversion film was prepared by dispersing a mixture of red pigment VQ-D25 and YAG : Ce3+ phosphor in PMMA. The authors have achieved a novel WOLED with the high color stability by optimizing the thickness and fluorescent pigment concentration of the color conversion film. When the driving voltage varied between 6 and 14 V, the color coordinates (CIE) varied slightly from (0.354, 0.304) to (0.357, 0.312) and the maximum current efficiency is about 5.8 cd x A(-1) (4.35 mA x cm(-2)), the maximum brightness is 16 800 cd x m(-2) at the operating voltage of 14 V.

Energy conversion in isothermal nonlinear irreversible processes - struggling for higher efficiency

NASA Astrophysics Data System (ADS)

Ebeling, W.; Feistel, R.

2017-06-01

First we discuss some early work of Ulrike Feudel on structure formation in nonlinear reactions including ions and the efficiency of the conversion of chemical into electrical energy. Then we give some survey about isothermal energy conversion from chemical to higher forms of energy like mechanical, electrical and ecological energy. Isothermal means here that there are no temperature gradients within the model systems. We consider examples of energy conversion in several natural processes and in some devices like fuel cells. Further, as an example, we study analytically the dynamics and efficiency of a simple "active circuit" converting chemical into electrical energy and driving currents which is roughly modeling fuel cells. Finally we investigate an analogous ecological system of Lotka-Volterra type consisting of an "active species" consuming some passive "chemical food". We show analytically for both these models that the efficiency increases with the load, reaches values higher then 50 percent in a narrow regime of optimal load and goes beyond some maximal load abruptly to zero.

Agricultural conversion without external water and nutrient inputs reduces terrestrial vegetation productivity

USGS Publications Warehouse

Smith, W. Kolby; Cleveland, Cory C.; Reed, Sasha C.; Running, Steven W.

2014-01-01

Driven by global population and standard of living increases, humanity co-opts a growing share of the planet's natural resources resulting in many well-known environmental trade-offs. In this study, we explored the impact of agriculture on a resource fundamental to life on Earth: terrestrial vegetation growth (net primary production; NPP). We demonstrate that agricultural conversion has reduced terrestrial NPP by ~7.0%. Increases in NPP due to agricultural conversion were observed only in areas receiving external inputs (i.e., irrigation and/or fertilization). NPP reductions were found for ~88% of agricultural lands, with the largest reductions observed in areas formerly occupied by tropical forests and savannas (~71% and ~66% reductions, respectively). Without policies that explicitly consider the impact of agricultural conversion on primary production, future demand-driven increases in agricultural output will likely continue to drive net declines in global terrestrial productivity, with potential detrimental consequences for net ecosystem carbon storage and subsequent climate warming.

Good distractions: Testing the effects of listening to an audiobook on driving performance in simple and complex road environments.

PubMed

Nowosielski, Robert J; Trick, Lana M; Toxopeus, Ryan

2018-02-01

Distracted driving (driving while performing a secondary task) causes many collisions. Most research on distracted driving has focused on operating a cell-phone, but distracted driving can include eating while driving, conversing with passengers or listening to music or audiobooks. Although the research has focused on the deleterious effects of distraction, there may be situations where distraction improves driving performance. Fatigue and boredom are also associated with collision risk and it is possible that secondary tasks can help alleviate the effects of fatigue and boredom. Furthermore, it has been found that individuals with high levels of executive functioning as measured by the OSPAN (Operation Span) task show better driving while multitasking. In this study, licensed drivers were tested in a driving simulator (a car body surrounded by screens) that simulated simple or complex roads. Road complexity was manipulated by increasing traffic, scenery, and the number of curves in the drive. Participants either drove, or drove while listening to an audiobook. Driving performance was measured in terms of braking response time to hazards (HRT): the time required to brake in response to pedestrians or vehicles that suddenly emerged from the periphery into the path of the vehicle, speed, standard deviation of speed, standard deviation of lateral position (SDLP). Overall, braking times to hazards were higher on the complex drive than the simple one, though the effects of secondary tasks such as audiobooks were especially deleterious on the complex drive. In contrast, on the simple drive, driving while listening to an audiobook lead to faster HRT. We found evidence that individuals with high OSPAN scores had faster HRTs when listening to an audiobook. These results suggest that there are environmental and individual factors behind difference in the allocation of attention while listening to audiobooks while driving. Copyright © 2017 Elsevier Ltd. All rights reserved.

Alcohol-Impaired Driving and Perceived Risks of Legal Consequences.

PubMed

Sloan, Frank A; McCutchan, Sabrina A; Eldred, Lindsey M

2017-02-01

Driving while impaired (DWI) is a threat to public health. Codified legal sanctions are a widely implemented strategy to reduce DWI. However, it is unclear that sanctioning affects individual risk perceptions so as to deter alcohol-impaired driving. Using survey data collected from individual drivers, police, and defense attorneys specializing in DWI in 8 U.S. cities, we investigated whether risk perceptions about legal consequences for alcohol-impaired driving, both the risk of being stopped if driving while alcohol-impaired and receiving specific penalties following a DWI, deter alcohol-impaired driving. First, we analyzed how different drivers' risk perceptions about being pulled over and facing criminal sanctions related to their self-reported alcohol-impaired driving in the year following the interview at which risk perceptions were elicited. Second, using data from an experimental module in which individual's risk perceptions were randomly updated by the interview, we analyzed how each driver's beliefs about his or her own future alcohol-impaired driving responded to randomly generated increases in the apprehension probability and sanction magnitude. Higher probabilities as estimated by the individuals of being pulled over corresponded to less alcohol-impaired driving in both analyses. Conversely, there was no statistical relationship between perceptions of criminal sanctions for DWI and alcohol-impaired driving with 1 exception-a small significant negative relationship between duration of jail time following a DWI conviction and alcohol-impaired driving. Perceptions regarding the threat of being apprehended for alcohol-impaired driving were related to actual self-reported driving, while perceived sanctions following a DWI conviction for DWI generally were unrelated to either actual self-reported alcohol-impaired driving or the person's estimate of probability that he or she would drive while alcohol-impaired in the following year. Increasing certainty of apprehension by increasing police staffing and/or conducting sobriety checks is a more effective strategy for reducing alcohol-impaired driving than legislating increased penalties for DWI. Copyright © 2017 by the Research Society on Alcoholism.

Alcohol-Impaired Driving and Perceived Risks of Legal Consequences

PubMed Central

Sloan, Frank A.; McCutchan, Sabrina A.; Eldred, Lindsey M.

2016-01-01

Background Driving while impaired (DWI) is a threat to public health. Codified legal sanctions are a widely-implemented strategy to reduce DWI. However, it is unclear that sanctioning affects individual risk perceptions so as to deter alcohol-impaired driving. Methods Using survey data collected from individual drivers, police, and defense attorneys specializing in DWI in eight U.S. cities, we investigated whether risk perceptions about legal consequences for alcohol-impaired driving, both the risk of being stopped if driving while alcohol-impaired and receiving specific penalties following a DWI, deter alcohol-impaired driving. First, we analyzed how different drivers’ risk perceptions about being pulled over and facing criminal sanctions related to their self-reported alcohol-impaired driving in the year following the interview at which risk perceptions were elicited. Second, using data from an experimental module in which individual’s risk perceptions were randomly updated by the interview, we analyzed how each driver’s beliefs about his or her own future alcohol-impaired driving responded to randomly-generated increases in the apprehension probability and sanction magnitude. Results Higher probabilities as estimated by the individuals of being pulled over corresponded to less alcohol-impaired driving in both analyses. Conversely, there was no statistical relationship between perceptions of criminal sanctions for DWI and alcohol-impaired driving with one exception—a small significant negative relationship between duration of jail time following a DWI conviction and alcohol-impaired driving. Conclusions Perceptions regarding the threat of being apprehended for alcohol-impaired driving were related to actual self-reported driving, while perceived sanctions following a DWI conviction for DWI generally were unrelated to either actual self-reported alcohol-impaired driving or the person’s estimate of probability that s/he would drive while alcohol-impaired in the following year. Increasing certainty of apprehension by increasing police staffing and/or conducting sobriety checks is a more effective strategy for reducing alcohol-impaired driving than legislating increased penalties for DWI. PMID:28056493

Flow Quality Studies of the NASA Glenn Research Center Icing Research Tunnel Circuit (1995 Tests)

NASA Technical Reports Server (NTRS)

Arrington, E. Allen; Kee-Bowling, Bonnie A.; Gonsalez, Jose C.

2000-01-01

The purpose of conducting the flow-field surveys described in this report was to more fully document the flow quality in several areas of the tunnel circuit in the NASA Glenn Research Center Icing Research Tunnel. The results from these surveys provide insight into areas of the tunnel that were known to exhibit poor flow quality characteristics and provide data that will be useful to the design of flow quality improvements and a new heat exchanger for the facility. An instrumented traversing mechanism was used to survey the flow field at several large cross sections of the tunnel loop over the entire speed range of the facility. Flow-field data were collected at five stations in the tunnel loop, including downstream of the fan drive motor housing, upstream and downstream of the heat exchanger, and upstream and downstream of the spraybars located in the settling chamber upstream of the test section. The data collected during these surveys greatly expanded the data base describing the flow quality in each of these areas. The new data matched closely the flow quality trends recorded from earlier tests. Data collected downstream of the heat exchanger and in the settling chamber showed how the configuration of the folded heat exchanger affected the pressure, velocity, and flow angle distributions in these areas. Smoke flow visualization was also used to qualitatively study the flow field in an area downstream of the drive fan and in the settling chamber/contraction section.

Conversion of energy in cross-sectional divergences under different conditions of inflow

NASA Technical Reports Server (NTRS)

Peters, H

1934-01-01

This investigation treats the conversion of energy in conically divergent channels with constant opening ratio and half included angle of from 2.6 to 90 degrees, the velocity distribution in the entrance section being varied from rectangular distribution to fully developed turbulence by changing the length of the approach. The energy conversion is not completed in the exit section of the diffuser; complete conversion requires a discharge length which depends upon the included angle and the velocity distribution in the entrance section. Lastly, a spiral fan was mounted in the extreme length and the effect of the spiral flow on the energy conversion in the cross-sectional divergence explored.

An entropy-based analysis of lane changing behavior: An interactive approach.

PubMed

Kosun, Caglar; Ozdemir, Serhan

2017-05-19

As a novelty, this article proposes the nonadditive entropy framework for the description of driver behaviors during lane changing. The authors also state that this entropy framework governs the lane changing behavior in traffic flow in accordance with the long-range vehicular interactions and traffic safety. The nonadditive entropy framework is the new generalized theory of thermostatistical mechanics. Vehicular interactions during lane changing are considered within this framework. The interactive approach for the lane changing behavior of the drivers is presented in the traffic flow scenarios presented in the article. According to the traffic flow scenarios, 4 categories of traffic flow and driver behaviors are obtained. Through the scenarios, comparative analyses of nonadditive and additive entropy domains are also provided. Two quadrants of the categories belong to the nonadditive entropy; the rest are involved in the additive entropy domain. Driving behaviors are extracted and the scenarios depict that nonadditivity matches safe driving well, whereas additivity corresponds to unsafe driving. Furthermore, the cooperative traffic system is considered in nonadditivity where the long-range interactions are present. However, the uncooperative traffic system falls into the additivity domain. The analyses also state that there would be possible traffic flow transitions among the quadrants. This article shows that lane changing behavior could be generalized as nonadditive, with additivity as a special case, based on the given traffic conditions. The nearest and close neighbor models are well within the conventional additive entropy framework. In this article, both the long-range vehicular interactions and safe driving behavior in traffic are handled in the nonadditive entropy domain. It is also inferred that the Tsallis entropy region would correspond to mandatory lane changing behavior, whereas additive and either the extensive or nonextensive entropy region would match discretionary lane changing behavior. This article states that driver behaviors would be in the nonadditive entropy domain to provide a safe traffic stream and hence with vehicle accident prevention in mind.

Variable-Displacement Hydraulic Drive Unit

NASA Technical Reports Server (NTRS)

Lang, D. J.; Linton, D. J.; Markunas, A.

1986-01-01

Hydraulic power controlled through multiple feedback loops. In hydraulic drive unit, power closely matched to demand, thereby saving energy. Hydraulic flow to and from motor adjusted by motor-control valve connected to wobbler. Wobbler angle determines motor-control-valve position, which in turn determines motor displacement. Concept applicable to machine tools, aircraft controls, and marine controls.

Rotating Biological Contactors (RBC's). Student Manual. Biological Treatment Process Control.

ERIC Educational Resources Information Center

Zickefoose, Charles S.

This student manual provides the textual material for a unit on rotating biological contactors (RBC's). Topic areas considered include: (1) flow patterns of water through RBC installations; (2) basic concepts (shaft and stage); (3) characteristics of biomass; (4) mechanical features (bearings, mechanical drive systems, and air drive systems); (5)…

In situ IR and X-ray high spatial-resolution microspectroscopy measurements of multistep organic transformation in flow microreactor catalyzed by Au nanoclusters.

PubMed

Gross, Elad; Shu, Xing-Zhong; Alayoglu, Selim; Bechtel, Hans A; Martin, Michael C; Toste, F Dean; Somorjai, Gabor A

2014-03-05

Analysis of catalytic organic transformations in flow reactors and detection of short-lived intermediates are essential for optimization of these complex reactions. In this study, spectral mapping of a multistep catalytic reaction in a flow microreactor was performed with a spatial resolution of 15 μm, employing micrometer-sized synchrotron-based IR and X-ray beams. Two nanometer sized Au nanoclusters were supported on mesoporous SiO2, packed in a flow microreactor, and activated toward the cascade reaction of pyran formation. High catalytic conversion and tunable products selectivity were achieved under continuous flow conditions. In situ synchrotron-sourced IR microspectroscopy detected the evolution of the reactant, vinyl ether, into the primary product, allenic aldehyde, which then catalytically transformed into acetal, the secondary product. By tuning the residence time of the reactants in a flow microreactor a detailed analysis of the reaction kinetics was performed. An in situ micrometer X-ray absorption spectroscopy scan along the flow reactor correlated locally enhanced catalytic conversion, as detected by IR microspectroscopy, to areas with high concentration of Au(III), the catalytically active species. These results demonstrate the fundamental understanding of the mechanism of catalytic reactions which can be achieved by the detailed mapping of organic transformations in flow reactors.

Wind from the black-hole accretion disk driving a molecular outflow in an active galaxy.

PubMed

Tombesi, F; Meléndez, M; Veilleux, S; Reeves, J N; González-Alfonso, E; Reynolds, C S

2015-03-26

Powerful winds driven by active galactic nuclei are often thought to affect the evolution of both supermassive black holes and their host galaxies, quenching star formation and explaining the close relationship between black holes and galaxies. Recent observations of large-scale molecular outflows in ultraluminous infrared galaxies support this quasar-feedback idea, because they directly trace the gas from which stars form. Theoretical models suggest that these outflows originate as energy-conserving flows driven by fast accretion-disk winds. Proposed connections between large-scale molecular outflows and accretion-disk activity in ultraluminous galaxies were incomplete because no accretion-disk wind had been detected. Conversely, studies of powerful accretion-disk winds have until now focused only on X-ray observations of local Seyfert galaxies and a few higher-redshift quasars. Here we report observations of a powerful accretion-disk wind with a mildly relativistic velocity (a quarter that of light) in the X-ray spectrum of IRAS F11119+3257, a nearby (redshift 0.189) optically classified type 1 ultraluminous infrared galaxy hosting a powerful molecular outflow. The active galactic nucleus is responsible for about 80 per cent of the emission, with a quasar-like luminosity of 1.5 × 10(46) ergs per second. The energetics of these two types of wide-angle outflows is consistent with the energy-conserving mechanism that is the basis of the quasar feedback in active galactic nuclei that lack powerful radio jets (such jets are an alternative way to drive molecular outflows).

Energy conversion modeling of the intrinsic persistent luminescence of solids via energy transfer paths between transition levels.

PubMed

Huang, Bolong; Sun, Mingzi

2017-04-05

An energy conversion model has been established for the intrinsic persistent luminescence in solids related to the native point defect levels, formations, and transitions. In this study, we showed how the recombination of charge carriers between different defect levels along the zero phonon line (ZPL) can lead to energy conversions supporting the intrinsic persistent phosphorescence in solids. This suggests that the key driving force for this optical phenomenon is the pair of electrons hopping between different charged defects with negative-U eff . Such a negative correlation energy will provide a sustainable energy source for electron-holes to further recombine in a new cycle with a specific quantum yield. This will help us to understand the intrinsic persistent luminescence with respect to native point defect levels as well as the correlations of electronics and energetics.

No drive line, no seal, no bearing and no wear: magnetics for impeller suspension and flow assessment in a new VAD.

PubMed

Huber, Christoph H; Tozzi, Piergiorgio; Hurni, Michel; von Segesser, Ludwig K

2004-06-01

The new magnetically suspended axial pump is free of seals, bearings, mechanical friction and wear. In the absence of a drive shaft or flow meter, pump flow assessment is made with an algorithm based on currents required for impeller rotation and stabilization. The aim of this study is to validate pump performance, algorithm-based flow and effective flow. A series of bovine experiments was realized after equipment with pressure transducers, continuous-cardiac-output-catheter, intracardiac ultrasound (AcuNav) over 6 h. Pump implantation was through a median sternotomy (LV-->VAD-->calibrated transonic-flow-probe-->aorta). A transonic-HT311-flow-probe was fixed onto the outflow cannula for flow comparison. Animals were electively sacrificed and at necropsy systematic pump inspection and renal embolus score was realized. Observation period was 340+/-62.4 min. The axial pump generated a mean arterial pressure of 58.8+/-14.3 mmHg (max 117 mmHg) running at a speed of 6591.3+/-1395.4 rev./min (min 5000/max 8500 rev./min) and generating 2.5+/-1.0 l/min (min 1.4/max 6.0 l/min) of flow. Correlation between the results of the pump flow algorithm and measured pump flow was linear (y=1.0339x, R2=0.9357). VAD explants were free of macroscopic thrombi. Renal embolus score was 0+/-0. The magnetically suspended axial flow pump provides excellent left ventricular support. The pump flow algorithm used is accurate and reliable. Therefore, there is no need for direct flow measurement.

Electroosmotic Flow Driven by DC and AC Electric Fields in Curved Microchannels

NASA Astrophysics Data System (ADS)

Chen, Jia-Kun; Luo, Win-Jet; Yang, Ruey-Jen

2006-10-01

The purpose of this study is to investigate electroosmotic flows driven by externally applied DC and AC electric fields in curved microchannels. For the DC electric driving field, the velocity distribution and secondary flow patterns are investigated in microchannels with various curvature ratios. We use the Dean number to describe the curvature effect of the flow field in DC electric field. The result implies that the effect of curvatures and the strength of the secondary flows become get stronger when the curvature ratio of C/A (where C is the radius of curvature of the microchannel and A is the half-height of rectangular curved tube.) is smaller. For the AC electric field, the velocity distribution and secondary flow patterns are investigated for driving frequencies in the range of 2.0 kHz (\\mathit{Wo}=0.71) to 11 kHz (\\mathit{Wo}=1.66). The numerical results reveal that the velocity at the center of the microchannel becomes lower at higher frequencies of the AC electric field and the strength of the secondary flow decreases. When the applied frequency exceeds 3.0 kHz (\\mathit{Wo}=0.87), vortices are no longer observed at the corners of the microchannel. Therefore, it can be concluded that the secondary flow induced at higher AC electric field frequencies has virtually no effect on the axial flow field in the microchannel.

Intrinsic Flow and Momentum Transport during Improved Confinement in MST

NASA Astrophysics Data System (ADS)

Craig, D.; Tan, E.; Schott, B.; Anderson, J. K.; Boguski, J.; Nornberg, M. D.; Xing, Z. A.

2017-10-01

Progress in absolute wavelength calibration of the Charge Exchange Recombination Spectroscopy (CHERS) system on MST has enabled new observations and analysis of intrinsic flow and momentum transport. Localized toroidal and poloidal flow measurements with systematic accuracy of +/- 3 km/s have been obtained during improved confinement Pulsed Parallel Current Drive (PPCD) plasmas at high plasma current (400-500 kA). The magnetic activity prior to and during the transition to improved confinement tends to increase the flow and sets the initial condition for the momentum profile evolution during improved confinement where intrinsic flow drive appears to weaken. Inboard flows change in time during PPCD, consistent with changes in the core-resonant m =1, n =6 tearing mode phase velocity. Outboard flows near the magnetic axis are time-independent, resulting in the development of a strongly sheared toroidal flow in the core and asymmetry in the poloidal flow profile. The deceleration of the n =6 mode during the period of improved confinement correlates well with the n =6 mode amplitude and is roughly consistent with the expected torque from eddy currents in the conducting shell. The level of Dα emission and secondary mode amplitudes (n =7-10) do not correlate with the mode deceleration suggesting that the momentum loss from charge exchange with neutrals and diffusion due to residual magnetic stochasticity are not significant in PPCD. This work has been supported by the U.S.D.O.E.

E  ×  B flow shear drive of the linear low-n modes of EHO in the QH-mode regime

NASA Astrophysics Data System (ADS)

Xu, G. S.; Wan, B. N.; Wang, Y. F.; Wu, X. Q.; Chen, Xi; Peng, Y.-K. Martin; Guo, H. Y.; Burrell, K. H.; Garofalo, A. M.; Osborne, T. H.; Groebner, R. J.; Wang, H. Q.; Chen, R.; Yan, N.; Wang, L.; Ding, S. Y.; Shao, L. M.; Hu, G. H.; Li, Y. L.; Lan, H.; Yang, Q. Q.; Chen, L.; Ye, Y.; Xu, J. C.; Li, J.

2017-08-01

A new model for the edge harmonic oscillations (EHOs) in the quiescent H-mode regime has been developed, which successfully reproduces the recent observations in the DIII-D tokamak. In particular, at high E  ×  B flow shear only a few low-n kink modes remain unstable at the plasma edge, consistent with the EHO behavior, while at low E  ×  B flow shear, the unstable mode spectrum is significantly broadened, consistent with the low-n broadband electromagnetic turbulence behavior. The model is based on a new mechanism for destabilizing low-n kink/peeling modes by the E  ×  B flow shear, which underlies the EHOs, separately from the previously found Kelvin-Helmholtz drive. We find that the differential advection of mode vorticity by sheared E  ×  B flows modifies the 2D pattern of mode electrostatic potential perpendicular to the magnetic field lines, which in turn causes a radial expansion of the mode structure, an increase of field line bending away from the mode rational surface, and a reduction of inertial stabilization. This enhances the kink drive as the parallel wavenumber increases significantly away from the rational surface at the plasma edge where the magnetic shear is also strong. This destabilization is also shown to be independent of the sign of the flow shear, as observed experimentally, and has not been taken into account in previous pedestal linear stability analyses. Verification of the veracity of this EHO mechanism will require analysis of the nonlinear evolution of low-n kink/peeling modes so destabilized in the linear regime.

The precession dynamo experiment at HZDR

NASA Astrophysics Data System (ADS)

Giesecke, A.; Gundrum, T.; Herault, J.; Stefani, F.; Gerbeth, G.

2015-12-01

In a next generation dynamo experiment currently under development atthe Helmholtz-Zentrum Dresden-Rossendorf (HZDR) a fluid flow of liquidsodium, solely driven by precession, will be considered as a possiblesource for magnetic field generation. The experiment is mainlymotivated by alternative concepts for astrophysical dynamos that arebased on mechanical flow driving. For example, it has long beendiscussed whether precession may be a complementary power source forthe geodynamo (Malkus, Science 1968) or for the ancient lunar dynamodue to the Earth-driven precession of the lunar spin axis (Dwyer, Nature 2011).We will present the current state of development of the dynamoexperiment together with results from non-linear hydrodynamicsimulations with moderate precessional forcing. Our simulations reveala non-axisymmetric forced mode with an amplitude of up to one fourthof the rotation velocity of the cylindrical container confirming thatprecession provides a rather efficient flow driving mechanism even atmoderate precession rates.More relevant for dynamo action might be free Kelvin modes (thenatural flow eigenmodes in a rotating cylinder) with higher azimuthalwave number. These modes may become relevant when constituting atriadic resonance with the fundamental forced mode, i.e., when theheight of the container matches their axial wave lengths. We findtriadic resonances at aspect ratios close to those predicted by thelinear theory except around the primary resonance of the forcedmode. In that regime we still identify free Kelvin modes propagatingin retrograde direction but none of them can be assigned to a triade.Our results will enter into the development of flow models that willbe used in kinematic simulations of the electromagnetic inductionequation in order to determine whether a precession driven flow willbe capable to drive a dynamo at all and to limit the parameter spacewithin which the occurrence of dynamo action is most promising.

The creation and influence of bifurcations and confluences in Hawaiian lava flows on conditions of flow emplacement

NASA Astrophysics Data System (ADS)

Dietterich, H. R.; Cashman, K. V.

2011-12-01

Hawaiian lava channels are characterized by numerous bifurcations and confluences that have important implications for flow behavior. The ubiquity of anastomosing flows, and their detailed observation over time, makes Hawai`i an ideal place to investigate the formation of these features and their effect on simple models of lava flow emplacement. Using a combination of high-resolution LiDAR data from the Kilauea December 1974 and Mauna Loa 1984 flows, orthoimagery of the Mauna Loa 1859 flow, and historical and InSAR mapping of the current eruption of Kilauea (1983-present), we quantify the geometry of distributary, anastomosing, and simple channel networks and compare these to flow advance rates and lengths. We use a pre-eruptive DEM of the Mauna Loa 1984 flow created from aerial photographs to investigate the relationship between underlying topography and channel morphology. In the Mauna Loa 1984 flow, the slope of the pre-eruptive surface correlates with the number of parallel channels. Slopes >4° generate up to thirteen parallel channels in contrast to slopes of <4° that produce fewer than eight parallel channels. In the 1983-1986 lava flows erupted from Pu`u `O`o, average effusion rate correlates with the number of bifurcations, each producing a new parallel channel. Flows with a volume flux <60 m3/s only have one bifurcation at most in the entire flow, while flows with a volume flux >60 m3/s contain up to four bifurcations. These data show that the splitting and merging of individual flows is a product of both the underlying ground surface and eruption rate. Important properties of the pre-eruptive topography include both the slope and the scale of surface roughness. We suggest that a crucial control is the height of the flow front in comparison to the scale of local topography and roughness. Greater slopes may create more active channels because the reduced flow thickness allows interaction with local obstacles of a greater size range. Conversely, higher viscosities could reduce the number of active channels by increasing the flow thickness. The effusion rate also influences the degree of flow branching, possibly by generating overflows and widening the flow. Branched channels can also rejoin at confluences, which occur on the leeward sides of obstacles and where the flow is confined against large-scale features, including fault scarps and older flow margins. We expect the maintenance of parallel channels past an obstacle that splits the flow to be a function of the slope and flux, which drives the flow downhill and governs the formation of levees. Our data reveal that by controlling the effective lava flux, bifurcations slow flow advance and restrict flow length. We postulate that flow branching may therefore restrict most Mauna Loa flow lengths to ~25 km, despite a wide range of effusion rates. In contrast, both confluences and the shut off of an active branch accelerate the flow. The complexity of Hawaiian flows has largely been ignored in predictive models of flow emplacement in Hawaii, but the flow geometries must be incorporated to improve syn-eruptive prediction of lava flow behavior.

Exhaust gas purification system for lean burn engine

DOEpatents

Haines, Leland Milburn

2002-02-19

An exhaust gas purification system for a lean burn engine includes a thermal mass unit and a NO.sub.x conversion catalyst unit downstream of the thermal mass unit. The NO.sub.x conversion catalyst unit includes at least one catalyst section. Each catalyst section includes a catalytic layer for converting NO.sub.x coupled to a heat exchanger. The heat exchanger portion of the catalyst section acts to maintain the catalytic layer substantially at a desired temperature and cools the exhaust gas flowing from the catalytic layer into the next catalytic section in the series. In a further aspect of the invention, the exhaust gas purification system includes a dual length exhaust pipe upstream of the NO.sub.x conversion catalyst unit. The dual length exhaust pipe includes a second heat exchanger which functions to maintain the temperature of the exhaust gas flowing into the thermal mass downstream near a desired average temperature.

Integrated Photoelectrochemical Solar Energy Conversion and Organic Redox Flow Battery Devices.

PubMed

Li, Wenjie; Fu, Hui-Chun; Li, Linsen; Cabán-Acevedo, Miguel; He, Jr-Hau; Jin, Song

2016-10-10

Building on regenerative photoelectrochemical solar cells and emerging electrochemical redox flow batteries (RFBs), more efficient, scalable, compact, and cost-effective hybrid energy conversion and storage devices could be realized. An integrated photoelectrochemical solar energy conversion and electrochemical storage device is developed by integrating regenerative silicon solar cells and 9,10-anthraquinone-2,7-disulfonic acid (AQDS)/1,2-benzoquinone-3,5-disulfonic acid (BQDS) RFBs. The device can be directly charged by solar light without external bias, and discharged like normal RFBs with an energy storage density of 1.15 Wh L -1 and a solar-to-output electricity efficiency (SOEE) of 1.7 % over many cycles. The concept exploits a previously undeveloped design connecting two major energy technologies and promises a general approach for storing solar energy electrochemically with high theoretical storage capacity and efficiency. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The total flow concept for geothermal energy conversion

NASA Technical Reports Server (NTRS)

Austin, A. L.

1974-01-01

A geothermal development project has been initiated at the Lawrence Livermore Laboratory (LLL) to emphasize development of methods for recovery and conversion of the energy in geothermal deposits of hot brines. Temperatures of these waters vary from 150 C to more than 300 C with dissolved solids content ranging from less than 0.1% to over 25% by weight. Of particular interest are the deposits of high-temperature/high-salinity brines, as well as less saline brines, known to occur in the Salton Trough of California. Development of this resource will depend on resolution of the technical problems of brine handling, scale and precipitation control, and corrosion/erosion resistant systems for efficient conversion of thermal to electrical energy. Research experience to date has shown these problems to be severe. Hence, the LLL program emphasizes development of an entirely different approach called the Total Flow concept.

Tears of Wine

NASA Astrophysics Data System (ADS)

Rathore, Prerana; Sharma, Vivek

`Tears of wine' refer to the rows of wine-drops that spontaneously emerge within a glass of strong wine. Evaporation-driven Marangoni flows near the meniscus of water-alcohol mixtures drive liquid upward forming a thin liquid film, and a rim or ridge forms near the moving contact line. Eventually the rim undergoes an instability forming drops, that roll back into bulk reservoir forming so called tears or legs of wine. Most studies in literature argue the evaporation of more volatile, lower surface tension component (alcohol) results in a concentration-dependent surface tension gradient that drives the climbing flow within the thin film. Though it is well-known that evaporative cooling can create temperature gradients that could provide additional contribution to the climbing flows, the role of thermocapillary flows is less well-understood. Furthermore, the patterns, flows and instabilities that occur near the rim, and determine the size and periodicity of tears, are not well-studied. Using experiments and theory, we visualize and analyze the formation and growth of tears of wine. The sliding drops, released from the rim towards the bulk reservoir, show oscillations and a cascade of fascinating flows that are analyzed for the first time.

From catastrophic acceleration to deceleration of liquid plugs in prewetted capillary tubes

NASA Astrophysics Data System (ADS)

Magniez, Juan; Baudoin, Michael; Zoueshtiagh, Farzam; Lemac/Lics Team

2016-11-01

Liquid/gas flows in capillaries are involved in a multitude of systems including flow in porous media, petroleum extraction, imbibition of paper or flows in pulmonary airways in pathological conditions. Liquid plugs, witch compose the biphasic flows, can have a dramatic impact on patients with pulmonary obstructive diseases, since they considerably alter the circulation of air in the airways and thus can lead to severe breathing difficulties. Here, the dynamics of liquid plugs in prewetted capillary tube is investigated experimentally and theoretically, with a particular emphasis on the role of the prewetting films and of the driving condition (constant flow rate, constant pressure). For both driving conditions, the plugs can either experience a continuous increase or decrease of their size. While this phenomenon is regular in the case of imposed flow rate, a constant pressure head can lead to a catastrophic acceleration of the plug and eventually its rupture or a dramatic increase of the plug size. A theoretical model is proposed to explain the transition between theses two regimes. These results give a new insight on the critical pressure required for airways obstruction and reopening. IEMN, International Laboratory LEMAC/LICS, UMR CNRS 8520, University of Lille.

Distracted Driving in Teens With and Without Attention-Deficit/Hyperactivity Disorder.

PubMed

Stavrinos, Despina; Garner, Annie A; Franklin, Crystal A; Johnson, Haley D; Welburn, Sharon C; Griffin, Russell; Underhill, Andrea T; Fine, Philip R

2015-01-01

This study is among the first to examine the effect of talking on a cell phone or text messaging while driving in teens with and without attention deficit/hyperactivity disorder (ADHD). Teens (average age 17years) with a diagnosis of ADHD (N=16) were matched with typically developing controls (N=18). All participants operated a driving simulator while (1) conversing on a cell phone, (2) text messaging, and (3) with no distraction during a baseline condition. Six indicators of driving performance were recorded: (a) time to complete the drive; (b) lane deviations; (c) variability in lane position (i.e., root mean square [RMS]); (d) reaction time; (e) motor vehicle collisions; and, (f) speed fluctuation. Significantly greater variation in lane position occurred in the texting task compared to no task and the cell phone task. While texting, in particular, teens with ADHD took significantly less time to complete the scenario. No significant main effects of group were found. Generally, those with ADHD did not differ in regard to driving performance, when compared to controls, with the exception of one outcome: time to complete scenario. These findings suggest that distracted driving impairs driving performance of teen drivers, regardless of ADHD status. Texting while driving had the greatest negative impact on driving performance, particularly with regard to variability in lane position (i.e., RMS). This study sheds light on key issues regarding injury prevention, with the intent of providing pediatric care providers with the knowledge to inform teen drivers of risks associated with distracted driving which will ultimately result in reduced rates of motor vehicle crashes and concomitant injuries. Published by Elsevier Inc.

Distracted Driving in Teens with and without Attention-Deficit/Hyperactivity Disorder

PubMed Central

Stavrinos, Despina; Garner, Annie A.; Franklin, Crystal A.; Johnson, Haley D.; Welburn, Sharon C.; Griffin, Russell; Underhill, Andrea T.; Fine, Philip R.

2015-01-01

Objective This study is among the first to examine the effect of talking on a cell phone or text messaging while driving in teens with and without Attention Deficit/Hyperactivity Disorder (ADHD). Method Teens (average age 17 years) with a diagnosis of ADHD (N=16) were matched with typically developing controls (N=18). All participants operated a driving simulator while (1) conversing on a cell phone, (2) text messaging, and (3) with no distraction during a baseline condition. Six indicators of driving performance were recorded: (a) time to complete the drive; (b) lane deviations; (c) variability in lane position (i.e., Root Mean Square [RMS]); (d) reaction time; (e) motor vehicle collisions; and, (f) speed fluctuation. Results Significantly greater variation in lane position occurred in the texting task compared to no task and the cell phone task. While texting, in particular, teens with ADHD took significantly less time to complete the scenario. No significant main effects of group were found. Conclusions Generally, those with ADHD did not differ in regard to driving performance, when compared to controls, with the exception of one outcome: time to complete scenario. These findings suggest that distracted driving impairs driving performance of teen drivers, regardless of ADHD status. Texting while driving had the greatest negative impact on driving performance, particularly with regard to variability in lane position (i.e., RMS). This study sheds light on key issues regarding injury prevention, with the intent of providing pediatric care providers with the knowledge to inform teen drivers of risks associated with distracted driving which will ultimately result in reduced rates of motor vehicle crashes and concomitant injuries. PMID:26049214

Passive margins getting squeezed in the mantle convection vice

NASA Astrophysics Data System (ADS)

Yamato, Philippe; Husson, Laurent; Becker, Thorsten W.; Pedoja, Kevin

2013-12-01

margins often exhibit uplift, exhumation, and tectonic inversion. We speculate that the compression in the lithosphere gradually increased during the Cenozoic, as seen in the number of mountain belts found at active margins during that period. Less clear is how that compression increase affects passive margins. In order to address this issue, we design a 2-D viscous numerical model wherein a lithospheric plate rests above a weaker mantle. It is driven by a mantle conveyor belt, alternatively excited by a lateral downwelling on one side, an upwelling on the other side, or both simultaneously. The lateral edges of the plate are either free or fixed, representing the cases of free convergence, and collision (or slab anchoring), respectively. This distinction changes the upper mechanical boundary condition for mantle circulation and thus, the stress field. Between these two regimes, the flow pattern transiently evolves from a free-slip convection mode toward a no-slip boundary condition above the upper mantle. In the second case, the lithosphere is highly stressed horizontally and deforms. For a constant total driving force, compression increases drastically at passive margins if upwellings are active. Conversely, if downwellings alone are activated, compression occurs at short distances from the trench and extension prevails elsewhere. These results are supported by Earth-like models that reveal the same pattern, where active upwellings are required to excite passive margins compression. Our results substantiate the idea that compression at passive margins is in response to the underlying mantle flow that is increasingly resisted by the Cenozoic collisions.

Conversion of umbilical arterial Doppler waveforms to cardiac cycle triggering signals: a preparatory study for online motion-gated three-dimensional fetal echocardiography.

PubMed

Deng, J; Birkett, A G; Kalache, K D; Hanson, M A; Peebles, D M; Linney, A D; Lees, W R; Rodeck, C H

2001-01-01

To remove motion artefacts, a device was built to convert "noisy" umbilical arterial Doppler waveforms (UADWs) from an ultrasound (US) system into sharp ECG R-wave-like cardiac cycle triggering signals (CCTSs). These CCTSs were then used to gate a simultaneous (online) 3-D acquisition of sectional fetal echocardiograms from another US system. To test the conversion performance, a study was carried out in sheep fetal twins. Pulmonary arterial flow waveforms (PAFWs) from implanted probes were traced, in the meantime, to determine the reference cardiac cycle. Interference caused by running the two nonsynchronised US systems was controlled to three degrees (not-noticeable, moderate, and severe), together with high (> or = 40 cm/s) and low (< 40) flow velocities on UADWs. The conversion efficiency, assessed by the percentage of UADWs converted into CCTSs, was in the range of 83% to 100% for not-noticeable and moderate interference, and 0% to 71% for severe interference. The triggering accuracy, assessed by [(time lag mean between the onsets of PAFWs and corresponding CCTSs) -- (its 99% confidence level)] / the mean, was 90% to 96% for the not-noticeable interference high- and low-flow groups and for the moderate interference high-flow group; 19% to 93% for the moderate interference low-flow group; and from not obtainable up to 90% for the severe interference groups. The results show that UADWs can be used as a satisfactory online motion-gating source even in the presence of moderate interference. The major problems are from severe interference or moderate interference with low-flow velocity, which can be minimised/eliminated by the integration of the individual systems involved.

Magnetic reconnection in Earth's magnetotail: Energy conversion and its earthward-tailward asymmetry

NASA Astrophysics Data System (ADS)

Lu, San; Pritchett, P. L.; Angelopoulos, V.; Artemyev, A. V.

2018-01-01

Magnetic reconnection, a fundamental plasma process, releases magnetic energy and converts it to particle energy, by accelerating and heating ions and electrons. This energy conversion plays an important role in the Earth's magnetotail. A two-dimensional particle-in-cell simulation is performed to study such a conversion in a magnetotail topology, one with a nonzero Bz, and the energy conversion is found to be more efficient in the earthward outflow than in the tailward outflow. Such earthward-tailward asymmetry is manifested not only in j .E but also in Poynting flux, Hall electromagnetic fields, bulk kinetic energy flux, enthalpy flux, heat flux, bulk acceleration, heating, and suprathermal particle energization, all of which are more prevalent on the earthward side. Such asymmetries are consistent with spacecraft observations reported in the literature. Our study shows that in the magnetotail, most of the energy converted by reconnection flows predominantly toward the Earth and has the potential of being geoeffective, rather than being expelled to the solar wind by the tailward flow. The energy conversion asymmetry arises from the presence of the non-zero normal magnetic field, the stronger lobe magnetic field, and the stronger cross-tail current earthward of the reconnection site in the pre-reconnecting thin current sheet.

Drivers of wetland conversion: a global meta-analysis.

PubMed

van Asselen, Sanneke; Verburg, Peter H; Vermaat, Jan E; Janse, Jan H

2013-01-01

Meta-analysis of case studies has become an important tool for synthesizing case study findings in land change. Meta-analyses of deforestation, urbanization, desertification and change in shifting cultivation systems have been published. This present study adds to this literature, with an analysis of the proximate causes and underlying forces of wetland conversion at a global scale using two complementary approaches of systematic review. Firstly, a meta-analysis of 105 case-study papers describing wetland conversion was performed, showing that different combinations of multiple-factor proximate causes, and underlying forces, drive wetland conversion. Agricultural development has been the main proximate cause of wetland conversion, and economic growth and population density are the most frequently identified underlying forces. Secondly, to add a more quantitative component to the study, a logistic meta-regression analysis was performed to estimate the likelihood of wetland conversion worldwide, using globally-consistent biophysical and socioeconomic location factor maps. Significant factors explaining wetland conversion, in order of importance, are market influence, total wetland area (lower conversion probability), mean annual temperature and cropland or built-up area. The regression analyses results support the outcomes of the meta-analysis of the processes of conversion mentioned in the individual case studies. In other meta-analyses of land change, similar factors (e.g., agricultural development, population growth, market/economic factors) are also identified as important causes of various types of land change (e.g., deforestation, desertification). Meta-analysis helps to identify commonalities across the various local case studies and identify which variables may lead to individual cases to behave differently. The meta-regression provides maps indicating the likelihood of wetland conversion worldwide based on the location factors that have determined historic conversions.

Drivers of Wetland Conversion: a Global Meta-Analysis

PubMed Central

van Asselen, Sanneke; Verburg, Peter H.; Vermaat, Jan E.; Janse, Jan H.

2013-01-01

Meta-analysis of case studies has become an important tool for synthesizing case study findings in land change. Meta-analyses of deforestation, urbanization, desertification and change in shifting cultivation systems have been published. This present study adds to this literature, with an analysis of the proximate causes and underlying forces of wetland conversion at a global scale using two complementary approaches of systematic review. Firstly, a meta-analysis of 105 case-study papers describing wetland conversion was performed, showing that different combinations of multiple-factor proximate causes, and underlying forces, drive wetland conversion. Agricultural development has been the main proximate cause of wetland conversion, and economic growth and population density are the most frequently identified underlying forces. Secondly, to add a more quantitative component to the study, a logistic meta-regression analysis was performed to estimate the likelihood of wetland conversion worldwide, using globally-consistent biophysical and socioeconomic location factor maps. Significant factors explaining wetland conversion, in order of importance, are market influence, total wetland area (lower conversion probability), mean annual temperature and cropland or built-up area. The regression analyses results support the outcomes of the meta-analysis of the processes of conversion mentioned in the individual case studies. In other meta-analyses of land change, similar factors (e.g., agricultural development, population growth, market/economic factors) are also identified as important causes of various types of land change (e.g., deforestation, desertification). Meta-analysis helps to identify commonalities across the various local case studies and identify which variables may lead to individual cases to behave differently. The meta-regression provides maps indicating the likelihood of wetland conversion worldwide based on the location factors that have determined historic conversions. PMID:24282580

The effects of text messaging on young drivers.

PubMed

Hosking, Simon G; Young, Kristie L; Regan, Michael A

2009-08-01

This study investigated the effects of using a cell phone to retrieve and send text messages on the driving performance of young novice drivers. Young drivers are particularly susceptible to driver distraction and have an increased risk of distraction-related crashes. Distractions from in-vehicle devices, particularly, those that require manual input, are known to cause decrements in driving performance. Twenty young novice drivers used a cell phone to retrieve and send text messages while driving a simulator. The amount of time that drivers spent not looking at the road when text messaging was up to approximately 400% greater than that recorded in baseline (notext-messaging) conditions. Furthermore, drivers' variability in lane position increased up to approximately 50%, and missed lane changes increased 140%. There was also an increase of up to approximately 150% in drivers' variability in following distances to lead vehicles. Previous research has shown that the risk of crashing while dialing a handheld device, such as when text messaging and driving, is more than double that of conversing on a cell phone. The present study has identified the detrimental effects of text messaging on driving performance that may underlie such increased crash risk. More effective road safety measures are needed to prevent and mitigate the adverse effects on driving performance of using cell phones to retrieve and send text messages.

Templated electrokinetic directed chemical assembly for the fabrication of close-packed plasmonic metamolecules

NASA Astrophysics Data System (ADS)

Thrift, W. J.; Darvishzadeh-Varcheie, M.; Capolino, F.; Ragan, R.

2017-08-01

Colloidal self-assembly combined with templated surfaces holds the promise of fabricating large area devices in a low cost facile manner. This directed assembly approach improves the complexity of assemblies that can be achieved with self-assembly while maintaining advantages of molecular scale control. In this work, electrokinetic driving forces, i.e., electrohydrodynamic flow, are paired with chemical crosslinking between colloidal particles to form close-packed plasmonic metamolecules. This method addresses challenges of obtaining uniformity in nanostructure geometry and nanometer scale gap spacings in structures. Electrohydrodynamic flows yield robust driving forces between the template and nanoparticles as well as between nanoparticles on the surface promoting the assembly of close-packed metamolecules. Here, electron beam lithography defined Au pillars are used as seed structures that generate electrohydrodynamic flows. Chemical crosslinking between Au surfaces enables molecular control over gap spacings between nanoparticles and Au pillars. An as-fabricated structure is analyzed via full wave electromagnetic simulations and shown to produce large magnetic field enhancements on the order of 3.5 at optical frequencies. This novel method for directed self-assembly demonstrates the synergy between colloidal driving forces and chemical crosslinking for the fabrication of plasmonic metamolecules with unique electromagnetic properties.

Mind the gap: a flow instability controlled by particle-surface distance

NASA Astrophysics Data System (ADS)

Driscoll, Michelle; Delmotte, Blaise; Youssef, Mena; Sacanna, Stefano; Donev, Aleksandar; Chaikin, Paul

2016-11-01

Does a rotating particle always spin in place? Not if that particle is near a surface: rolling leads to translational motion, as well as very strong flows around the particle, even quite far away. These large advective flows strongly couple the motion of neighboring particles, giving rise to strong collective effects in groups of rolling particles. Using a model experimental system, weakly magnetic colloids driven by a rotating magnetic field, we observe that driving a compact group of microrollers leads to a new kind of flow instability. First, an initially uniformly-distributed strip of particles evolves into a shock structure, and then it becomes unstable, emitting fingers with a well-defined wavelength. Using 3D large-scale simulations in tandem with our experiments, we find that the instability wavelength is controlled not by the driving torque or the fluid viscosity, but a geometric parameter: the microroller's distance above the container floor. Furthermore, we find that the instability dynamics can be reproduced using only one ingredient: hydrodynamic interactions near a no-slip boundary.

The modulational instability in the extended Hasegawa-Mima equation with a finite Larmor radius

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gallagher, S.; Hnat, B.; Rowlands, G.

2012-12-15

The effects of the finite Larmor radius on the generation of zonal flows by the four-wave modulational instability are investigated using an extended form of the Hasegawa-Mima equation. Growth rates of the zonal mode are quantified using analytical predictions from a four-mode truncated model, as well as from direct numerical simulation of the nonlinear extended Hasegawa-Mima equation. We not only consider purely zonal flows but also examine the generic oblique case and show that, for small Larmor radii, off-axis modes may become dominant. We find a key parameter M{sub {rho}} which characterises the behaviour of the system due to changesmore » in the Larmor radius. We find that, similarly to previous results obtained by changing the driving wave amplitude, two separate dynamical regimes can be accessed. These correspond to oscillatory energy transfer between zonal flows and a driving wave and the fully saturated zonal flow.« less

An Integrated Approach to Conversion, Verification, Validation and Integrity of AFRL Generic Engine Model and Simulation (Postprint)

DTIC Science & Technology

2007-02-01

and Astronautics 11 PS3C W3 P3 T3 FAR3 Ps3 W41 P41 T41 FAR41 Ps41 W4 P4 T4 FAR4 Ps4 7 NozFlow 6 Flow45 5 Flow44 4 Flow41 3 Flow4 2 Flow3 1 N2Bal... Motivation for Modeling and Simulation Work The Augmented Generic Engine Model (AGEM) Model Verification and Validation (V&V) Assessment of AGEM V&V

Fundamental Physics and Practical Applications of Electromagnetic Local Flow Control in High Speed Flows (Rutgers)

DTIC Science & Technology

2010-02-16

field. Techniques utilizing this design use an open- loop control and no flow monitoring sensors are required. Conversely, reactive (or closed - loop ...and closed (dashed line) configuration. 38 closed configuration described above, the ambiguity in the critical limits of the transition...flow; a new vortex is then shed from the cavity leading edge, closing the feedback loop .[31] Open cavities with an L/D approximately greater than

Automated Driving System Architecture to Ensure Safe Delegation of Driving Authority

NASA Astrophysics Data System (ADS)

YUN, Sunkil; NISHIMURA, Hidekazu

2016-09-01

In this paper, the architecture of an automated driving system (ADS) is proposed to ensure safe delegation of driving authority between the ADS and a driver. Limitations of the ADS functions may activate delegation of driving authority to a driver. However, it leads to severe consequences in emergency situations where a driver may be drowsy or distracted. To address these issues, first, the concept model for the ADS in the situation for delegation of driving authority is described taking the driver's behaviour and state into account. Second, the behaviour / state of a driver and functional flow / state of ADS and the interactions between them are modelled to understand the context where the ADS requests to delegate the driving authority to a driver. Finally, the proposed architecture of the ADS is verified under the simulations based on the emergency braking scenarios. In the verification process using simulation, we have derived the necessary condition for safe delegation of driving authority is that the ADS should assist s driver even after delegating driving authority to a driver who has not enough capability to regain control of the driving task.

Phone Conversation while Processing Information: Chronometric Analysis of Load Effects in Everyday-media Multitasking

PubMed Central

Steinborn, Michael B.; Huestegge, Lynn

2017-01-01

This is a pilot study that examined the effect of cell-phone conversation on cognition using a continuous multitasking paradigm. Current theorizing argues that phone conversation affects behavior (e.g., driving) by interfering at a level of cognitive processes (not peripheral activity) and by implying an attentional-failure account. Within the framework of an intermittent spare–utilized capacity threading model, we examined the effect of aspects of (secondary-task) phone conversation on (primary-task) continuous arithmetic performance, asking whether phone use makes components of automatic and controlled information-processing (i.e., easy vs. hard mental arithmetic) run more slowly, or alternatively, makes processing run less reliably albeit with the same processing speed. The results can be summarized as follows: While neither expecting a text message nor expecting an impending phone call had any detrimental effects on performance, active phone conversation was clearly detrimental to primary-task performance. Crucially, the decrement imposed by secondary-task (conversation) was not due to a constant slowdown but is better be characterized by an occasional breakdown of information processing, which differentially affected automatic and controlled components of primary-task processing. In conclusion, these findings support the notion that phone conversation makes individuals not constantly slower but more vulnerable to commit attention failure, and in this way, hampers stability of (primary-task) information processing. PMID:28634458

Phone Conversation while Processing Information: Chronometric Analysis of Load Effects in Everyday-media Multitasking.

PubMed

Steinborn, Michael B; Huestegge, Lynn

2017-01-01

This is a pilot study that examined the effect of cell-phone conversation on cognition using a continuous multitasking paradigm. Current theorizing argues that phone conversation affects behavior (e.g., driving) by interfering at a level of cognitive processes (not peripheral activity) and by implying an attentional-failure account. Within the framework of an intermittent spare-utilized capacity threading model, we examined the effect of aspects of (secondary-task) phone conversation on (primary-task) continuous arithmetic performance, asking whether phone use makes components of automatic and controlled information-processing (i.e., easy vs. hard mental arithmetic) run more slowly, or alternatively, makes processing run less reliably albeit with the same processing speed. The results can be summarized as follows: While neither expecting a text message nor expecting an impending phone call had any detrimental effects on performance, active phone conversation was clearly detrimental to primary-task performance. Crucially, the decrement imposed by secondary-task (conversation) was not due to a constant slowdown but is better be characterized by an occasional breakdown of information processing, which differentially affected automatic and controlled components of primary-task processing. In conclusion, these findings support the notion that phone conversation makes individuals not constantly slower but more vulnerable to commit attention failure, and in this way, hampers stability of (primary-task) information processing.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaufman, A.N.; Morehead, J.J.; Brizard, A.J.

Linear conversion of an incoming magnetosonic wave (a.k.a. fast or compressional wave) to an ion-hybrid wave can be considered as a 3-step process in ray phase space. This is demonstrated by casting the cold-fluid model into the Friedland-Kaufman normal form for linear mode conversion. First, the incoming magnetosonic ray (MSR) converts a fraction of its action to an {ital intermediate} ion-hybrid ray (IHR), with the transmitted ray proceeding through the conversion layer. The IHR propagates in k-space to a {ital second} conversion point, where it converts in turn a fraction of its action into a {ital reflected} MSR, with themore » remainder of the its action constituting the {ital converted} IHR. The modular approach gives {ital exact} agreement with the more standard Budden formulation for the transmission, reflection and conversion coefficients, but has the important advantage of exposing the intermediate IHR. The existence of the intermediate IHR has important physical consequences as it can resonate with {alpha} particles. We estimate the time-integrated damping coefficient between the two conversions and show that {integral}{gamma}dt is of order {minus}100, thus the IH wave is completely annihilated between conversions and transfers its energy to the {alpha}{close_quote}s. This suggests that proposals to use the IH mode for current drive or DT heating are likely to fail in the presence of fusion {alpha}{close_quote}s. {copyright} {ital 1997 American Institute of Physics.}« less

Physical and numerical aspects of the high-speed unsteady flow around concave axisymmetric bodies

NASA Astrophysics Data System (ADS)

Panaras, Argyris; Drikakis, Dimitris

2011-09-01

The axisymmetric concave body is a typical configuration about which shock/shock interactions appear. Various shapes of axisymmetric concave bodies are used in a variety of applications in aeronautics, for example, axisymmetric jet inlets with conical centerbody, ballistic missiles drag reduction by spike, plasma or hot gas injection, parachutes for pilot-ejection capsules. However, it is well known that two distinct modes of instability appear around a concave body in the high-speed flow regime for a certain range of geometric parameters. These instabilities can cause undesirable effects such as severe vibration of the structure, heating and pressure loads. According to the experimental evidence, the unsteady flow is characterised by periodic radial inflation and collapse of the conical separation bubble formed around the forebody (pulsation). Various explanations have been given for the driving mechanism of the instabilities. In the present, merging of the leading explanations is done, and basic rules for the passive suppression of the instabilities are applied, in order to enforce their proposed driving. In addition, the effect of the flow initialisation method on the flow structure predicted by numerical simulations is examined. For certain configurations, bifurcation of the time-dependent flow has been found. This behaviour is explained with recourse to the phenomenon of hysteresis, which is an inherent feature of the examined flows.

Streaming driven by sessile microbubbles: Explaining flow patterns and frequency response

NASA Astrophysics Data System (ADS)

Rallabandi, Bhargav; Wang, Cheng; Guo, Lin; Hilgenfeldt, Sascha

2013-11-01

Ultrasound excitation of bubbles drives powerful steady streaming flows which have found widespread applications in microfluidics, where bubbles are typically of semicircular cross section and attached to walls of the device (sessile). While bubble-driven streaming in bulk fluid is well understood, this practically relevant case presents additional complexity introduced by the wall and contact lines. We develop an asymptotic theory that takes into account the presence of the wall as well as the oscillation dynamics of the bubble, providing a complete description of the streaming flow as a function only of the driving frequency, the bubble size, and the physical properties of the fluid. We show that the coupling between different bubble oscillation modes sustains the experimentally observed streaming flow vortex pattern over a broad range of frequencies, greatly exceeding the widths of individual mode resonances. Above a threshold frequency, we predict, and observe in experiment, reversal of the flow direction. Our analytical theory can be used to guide the design of microfluidic devices, both in situations where robust flow patterns insensitive to parameter changes are desired (e.g. lab-on-a-chip sorters), and in cases where intentional modulation of the flow field appearance is key (e.g. efficient mixers). Current address: Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology.

Rotation Motion of Designed Nano-Turbine

PubMed Central

Li, Jingyuan; Wang, Xiaofeng; Zhao, Lina; Gao, Xingfa; Zhao, Yuliang; Zhou, Ruhong

2014-01-01

Construction of nano-devices that can generate controllable unidirectional rotation is an important part of nanotechnology. Here, we design a nano-turbine composed of carbon nanotube and graphene nanoblades, which can be driven by fluid flow. Rotation motion of nano-turbine is quantitatively studied by molecular dynamics simulations on this model system. A robust linear relationship is achieved with this nano-turbine between its rotation rate and the fluid flow velocity spanning two orders of magnitude, and this linear relationship remains intact at various temperatures. More interestingly, a striking difference from its macroscopic counterpart is identified: the rotation rate is much smaller (by a factor of ~15) than that of the macroscopic turbine with the same driving flow. This discrepancy is shown to be related to the disruption of water flow at nanoscale, together with the water slippage at graphene surface and the so-called “dragging effect”. Moreover, counterintuitively, the ratio of “effective” driving flow velocity increases as the flow velocity increases, suggesting that the linear dependence on the flow velocity can be more complicated in nature. These findings may serve as a foundation for the further development of rotary nano-devices and should also be helpful for a better understanding of the biological molecular motors. PMID:25068725

Optimistic honesty: understanding surgeon and patient perspectives on hopeful communication in pancreatic cancer care.

PubMed

Blakely, Kim; Karanicolas, Paul J; Wright, Frances C; Gotlib Conn, Lesley

2017-07-01

Prognosis conversations between surgical oncologists and patients with pancreatic cancer are critically important and challenging. Surgeons and their patients often have discrepant understandings of prognosis despite extensive conversations. Little is known about how surgeons approach prognosis conversations with these patients; patients' experiences with these conversations are also not well understood. This qualitative study sought to better understand surgeon and patient perspectives on communication in pancreatic cancer care with a view toward improvement. Grounded theory methodology was used. Semi-structured interviews were conducted with surgical oncologists and patients who had undergone surgical resection with curative intent for periampullary cancer. Data were collected and analyzed inductively and iteratively to the point of theoretical saturation. 10 surgeons and 10 patients participated. Three inter-linking concepts were found to drive surgeon-patient conversations: understanding, trust and hope. Surgeons delicately and purposefully tailored information for patients, striving to deliver essential though honest, empathetic and hopeful messages. Patients desired simple, truthful explanations that demonstrated caring and fostered optimism. Surgeons and patients with pancreatic cancer value optimistic honesty in tailored prognosis conversations. Perceived discrepancies in surgeon-patient understanding must be contextualized within efforts to establish a sufficient understanding, high level of trust, and optimistic stance of hope. Copyright © 2017 International Hepato-Pancreato-Biliary Association Inc. Published by Elsevier Ltd. All rights reserved.

Energy transfer model and its applications of ultrasonic gas flow-meter under static and dynamic flow rates

NASA Astrophysics Data System (ADS)

Fang, Min; Xu, Ke-Jun; Zhu, Wen-Jiao; Shen, Zi-Wen

2016-01-01

Most of the ultrasonic gas flow-meters measure the gas flow rate by calculating the ultrasonic transmission time difference between the downstream and upstream. Ultrasonic energy attenuation occurs in the processes of the ultrasonic generation, conversion, transmission, and reception. Additionally, at the same time, the gas flow will also affect the ultrasonic propagation during the measurement, which results in the ultrasonic energy attenuation and the offset of ultrasonic propagation path. Thus, the ultrasonic energy received by the transducer is weaker. When the gas flow rate increases, this effect becomes more apparent. It leads to the measurement accuracy reduced, and the measurement range narrowed. An energy transfer model, where the ultrasonic gas flow-meter under without/with the gas flow, is established by adopting the statistical analysis and curve fitting based on a large amount of experimental data. The static sub model without the gas flow expresses the energy conversion efficiency of ultrasonic gas transducers, and the dynamic sub model with the gas flow reflects the energy attenuation pattern following the flow rate variations. The mathematical model can be used to determine the minimum energy of the excitation signal for meeting the requirement of specific measurement range, and predict the maximum measurable flow rate in the case of fixed energy of excitation signal. Based on the above studies, a method to enhance the excitation signal energy is proposed under the output power of the transmitting circuit being a finite value so as to extend the measurement rage of ultrasonic gas flow-meter.

The in situ generation and reactive quench of diazonium compounds in the synthesis of azo compounds in microreactors.

PubMed

Akwi, Faith M; Watts, Paul

2016-01-01

In this paper, a micro-fluidic optimized process for the continuous flow synthesis of azo compounds is presented. The continuous flow synthesis of Sudan II azo dye was used as a model reaction for the study. At found optimal azo coupling reaction temperature and pH an investigation of the optimum flow rates of the reactants for the diazotization and azo coupling reactions in Little Things Factory-MS microreactors was performed. A conversion of 98% was achieved in approximately 2.4 minutes and a small library of azo compounds was thus generated under these reaction conditions from couplers with aminated or hydroxylated aromatic systems. The scaled up synthesis of these compounds in PTFE tubing (i.d. 1.5 mm) was also investigated, where good reaction conversions ranging between 66-91% were attained.

Marine current energy conversion: the dawn of a new era in electricity production.

PubMed

Bahaj, AbuBakr S

2013-02-28

Marine currents can carry large amounts of energy, largely driven by the tides, which are a consequence of the gravitational effects of the planetary motion of the Earth, the Moon and the Sun. Augmented flow velocities can be found where the underwater topography (bathymetry) in straits between islands and the mainland or in shallows around headlands plays a major role in enhancing the flow velocities, resulting in appreciable kinetic energy. At some of these sites where practical flows are more than 1 m s(-1), marine current energy conversion is considered to be economically viable. This study describes the salient issues related to the exploitation of marine currents for electricity production, resource assessment, the conversion technologies and the status of leading projects in the field. This study also summarizes important issues related to site development and some of the approaches currently being undertaken to inform device and array development. This study concludes that, given the highlighted commitments to establish favourable regulatory and incentive regimes as well as the aspiration for energy independence and combating climate change, the progress to multi-megawatt arrays will be much faster than that achieved for wind energy development.

Time-dependent electrokinetic flows of non-Newtonian fluids in microchannel-array for energy conversion

NASA Astrophysics Data System (ADS)

Chun, Myung-Suk; Chun, Byoungjin; Lee, Ji-Young; Complex Fluids Team

2016-11-01

We investigate the externally time-dependent pulsatile electrokinetic viscous flows by extending the previous simulations concerning the electrokinetic microfluidics for different geometries. The external body force originated from between the nonlinear Poisson-Boltzmann field and the flow-induced electric field is employed in the Cauchy momentum equation, and then the Nernst-Planck equation in connection with the net current conservation is coupled. Our explicit model allows one to quantify the effects of the oscillating frequency and conductance of the Stern layer, considering the shear thinning effect and the strong electric double layer interaction. This presentation reports the new results regarding the implication of optimum frequency pressure pulsations toward realizing mechanical to electrical energy transfer with high conversion efficiencies. These combined factors for different channel dimension are examined in depth to obtain possible enhancements of streaming current, with taking advantage of pulsating pressure field. From experimental verifications by using electrokinetic power chip, it is concluded that our theoretical framework can serve as a useful basis for micro/nanofluidics design and potential applications to the enhanced energy conversion. NRF of Korea (No.2015R1A2A1A15052979) and KIST (No.2E26490).

Top-down methodology for human factors research

NASA Technical Reports Server (NTRS)

Sibert, J.

1983-01-01

User computer interaction as a conversation is discussed. The design of user interfaces which depends on viewing communications between a user and the computer as a conversion is presented. This conversation includes inputs to the computer (outputs from the user), outputs from the computer (inputs to the user), and the sequencing in both time and space of those outputs and inputs. The conversation is viewed from the user's side of the conversation. Two languages are modeled: the one with which the user communicates with the computer and the language where communication flows from the computer to the user. Both languages exist on three levels; the semantic, syntactic and lexical. It is suggested that natural languages can also be considered in these terms.

Speak up or Burn out: Five Crucial Conversations that Drive Educational Excellence

ERIC Educational Resources Information Center

Maxfield, David

2009-01-01

Challenges such as overcrowded classrooms, poor administrative and parental support, loss of control in the classroom, and bureaucratic red tape are enough to make any teacher abandon the fight for educational excellence and run for the ridge. When teachers retreat, they cross a line between simple stress and serious burnout. In burnout, their…

The economic drivers behind residential conversion in the oak woodlands

Treesearch

William Stewart; James Spero; Shawn Saving

2008-01-01

Acre for acre, oak woodlands provide habitats for a greater range of wildlife species than grasslands and irrigated agricultural lands. Oak woodlands also are highly valued as open space around residential development. The rich habitat diversity and the physical attractiveness drives residential interest in living in or adjacent to oak woodlands as well as preservation...

Grassland restoration following mesquite invasion in the northern Chihuahuan Desert: Persistence, patience, and perspectives from the past and present

USDA-ARS?s Scientific Manuscript database

The widespread invasion of grasslands by woody plants in the northern Chihuahuan Desert over the past 100-150 years is well-documented, and has stimulated a large body of research about the mechanisms driving this conversion, as well as approaches to grassland restoration. Progressive invasion and e...

Consequences of cognitive impairments following traumatic brain injury: Pilot study on visual exploration while driving.

PubMed

Milleville-Pennel, Isabelle; Pothier, Johanna; Hoc, Jean-Michel; Mathé, Jean-François

2010-01-01

The aim was to assess the visual exploration of a person suffering from traumatic brain injury (TBI). It was hypothesized that visual exploration could be modified as a result of attentional or executive function deficits that are often observed following brain injury. This study compared an analysis of eyes movements while driving with data from neuropsychological tests. Five participants suffering from TBI and six control participants took part in this study. All had good driving experience. They were invited to drive on a fixed-base driving simulator. Eye fixations were recorded using an eye tracker. Neuropsychological tests were used to assess attention, working memory, rapidity of information processing and executive functions. Participants with TBI showed a reduction in the variety of the visual zones explored and a reduction of the distance of exploration. Moreover, neuropsychological evaluation indicates that there were difficulties in terms of divided attention, anticipation and planning. There is a complementarity of the information obtained. Tests give information about cognitive deficiencies but not about their translation into a dynamic situation. Conversely, visual exploration provides information about the dynamic with which information is picked up in the environment but not about the cognitive processes involved.

Concurrent processing of vehicle lane keeping and speech comprehension tasks.

PubMed

Cao, Shi; Liu, Yili

2013-10-01

With the growing prevalence of using in-vehicle devices and mobile devices while driving, a major concern is their impact on driving performance and safety. However, the effects of cognitive load such as conversation on driving performance are still controversial and not well understood. In this study, an experiment was conducted to investigate the concurrent performance of vehicle lane keeping and speech comprehension tasks with improved experimental control of the confounding factors identified in previous studies. The results showed that the standard deviation of lane position (SDLP) was increased when the driving speed was faster (0.30 m at 36 km/h; 0.36 m at 72 km/h). The concurrent comprehension task had no significant effect on SDLP (0.34 m on average) or the standard deviation of steering wheel angle (SDSWA; 5.20° on average). The correct rate of the comprehension task was reduced in the dual-task condition (from 93.4% to 91.3%) compared with the comprehension single-task condition. Mental workload was significantly higher in the dual-task condition compared with the single-task conditions. Implications for driving safety were discussed. Copyright © 2013 Elsevier Ltd. All rights reserved.

Investigation of mechanisms linking media exposure to smoking in high school students.

PubMed

Carson, Nicholas J; Rodriguez, Daniel; Audrain-McGovern, Janet

2005-08-01

Media exposure has been found to impact adolescent smoking, although the mechanisms of this relationship have not been thoroughly investigated. Drive for thinness and tobacco advertising receptivity, both shown to be associated with smoking, are two potential mediators. 967 twelfth grade students completed a self-report survey as part of a longitudinal study of biobehavioral predictors of smoking. Exposure to magazines and television, drive for thinness, tobacco advertisement receptivity, and twelfth grade smoking level were the primary variables of interest. Effects of gender, race, BMI, smoking exposure, and perceived physical appearance were controlled for in the model. Exposure to fashion, entertainment, and gossip magazines had indirect effects on smoking via drive for thinness and tobacco advertisement receptivity. There was a direct effect of health, fitness, and sports magazine reading on smoking. Television watching had no significant effects on smoking. Adolescents who read fashion, entertainment, and gossip magazines may be more likely to smoke, in part, because of a higher drive for thinness and greater receptivity to cigarette advertisements. Conversely, adolescents reading Health and Fitness magazines may be less likely to smoke. Drive for thinness and tobacco advertising receptivity are thus potential targets for adolescent smoking intervention.

Potential for Increasing the Output of Existing Hydroelectric Plants.

DTIC Science & Technology

1981-06-01

existing units to higher generating capacity by rehabilitating, modifying or replacing turbines and/or generators; increasing the effective...loss in converting fluid energy (flow and head) to mechanical energy ( turbine output) to electrical energy (generator output). The significant practical...opportunity is improvement of the energy conversion efficiency of the hydraulic turbine since the energy conversion efficiency of electrical

Flow Shears at the Poleward Boundary of Omega Bands Observed During Conjunctions of Swarm and THEMIS ASI

NASA Astrophysics Data System (ADS)

Liu, Jiang; Lyons, L. R.; Archer, W. E.; Gallardo-Lacourt, B.; Nishimura, Y.; Zou, Ying; Gabrielse, C.; Weygand, J. M.

2018-02-01

Omega bands are curved aurora forms that evolve from a quiet arc located along the poleward edge of a diffuse auroral band within the midnight to morningside auroral oval. They usually propagate eastward. Because omega bands are a significant contributor to an active magnetotail, knowledge about their generation is important for understanding tail dynamics. Previous studies have shown that auroral streamers, footprints of fast flows in the tail, can propagate into omega bands. Such events, however, are limited, and it is still unclear whether and how the flows trigger the bands. The ionospheric flows associated with omega bands may provide valuable information on the driving mechanisms of the bands. We examine these flows taking advantage of the conjunctions between the Swarm spacecraft and Time History of Events and Macroscale Interactions during Substorms all-sky imagers, which allow us to demonstrate the relative location of the flows to the omega bands' bright arcs for the first time. We find that a strong eastward ionospheric flow is consistently present immediately poleward of the omega band's bright arc, resulting in a sharp flow shear near the poleward boundary of the band. This ionospheric flow shear should correspond to a flow shear near the inner edge of the plasma sheet. This plasma sheet shear may drive a Kelvin-Helmholz instability which then distorts the quiet arc to form omega bands. It seems plausible that the strong eastward flows are driven by streamer-related fast flows or enhanced convection in the magnetotail.

Quasielastic neutron scattering with in situ humidity control: Water dynamics in uranyl fluoride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miskowiec, A., E-mail: miskowiecaj@ornl.gov; Trowbridge, L.; Anderson, B.

2016-03-07

The structural phase diagram of uranyl fluoride (UO{sub 2}F{sub 2}), while incomplete, contains at least one anhydrous crystal structure and a second, zeolite-like structure with the formula [(UO{sub 2}F{sub 2})(H{sub 2}O)]{sub 7} ⋅ (H{sub 2}O){sub 4} that can be produced by adding water to the anhydrous structure. While traditional diffraction measurements can easily differentiate these crystals, additional aqueous structures (in general of the form UO{sub 2}F{sub 2} + xH{sub 2}O) have been proposed as well. We present results using a novel sample environment setup to intercalate water during a quasielastic neutron scattering measurement over the course of 86 h. Our sample environment allows low-pressure (<2 atm)more » humid air flow across the sample coupled with a system to control the relative humidity of this air flow between 10% and 70%. The water dynamics in UO{sub 2}F{sub 2} and [(UO{sub 2}F{sub 2})(H{sub 2}O)]{sub 7} ⋅ (H{sub 2}O){sub 4} are sufficiently different to distinguish them, with water in the latter executing a restricted diffusion (D = 2.7 × 10{sup −6} cm{sup 2}/s) within the structure's accessible pores (r = 3.17 Å) such that the dynamics can be used as a fingerprinting tool. We confirm that water vapor pressure is the driving thermodynamic force for the conversion of the anhydrous structure to [(UO{sub 2}F{sub 2})(H{sub 2}O)]{sub 7} ⋅ (H{sub 2}O){sub 4}, and we demonstrate the feasibility of extending this approach to aqueous forms of UO{sub 2}F{sub 2} + xH{sub 2}O. This method has general applicability to systems in which water content itself is a driving variable for structural or dynamical phase transitions.« less

Research on traffic flow characteristics at signal intersection

NASA Astrophysics Data System (ADS)

Zeng, Jun-Wei; Yu, Sen-Bin; Qian, Yong-Sheng; Wei, Xu-Ting; Feng, Xiao; Wang, Hui

2017-09-01

Based on the cautious driving behavior and the principle of the vehicles at left-side having priority to pass in the intersection, a two-dimensional cellular automata model for planar signalized intersection (NS-STCA) is established. The different turning vehicles are regarded as the research objects and the effect of the left-turn probability, signal cycle, vehicle flow density on traffic flow at the intersection is investigated.

Liquid crystal dynamic flow control by bidirectional alignment surface

NASA Astrophysics Data System (ADS)

Li, Y. W.; Lee, C. Y.; Kwok, H. S.

2009-02-01

We investigate the behavior of liquid crystal dynamic flow in a cell with a bidirectional alignment (BDA) surface. Numerical simulations show that with a BDA surface having a pitch comparable to the cell gap d, the liquid crystal dynamic flow direction can be controlled by the driving voltage. Such an effect can be applied to bistable twisted nematic displays without the need for anchoring breaking.

A Market, Operation, and Mission Assessment of Large Rural For-Profit Hospitals with Positive Cash Flow

ERIC Educational Resources Information Center

McCue, Michael J.

2007-01-01

Context: National benchmark data for 2002 indicate that large rural for-profit hospitals have a median cash flow margin of 19.5% compared to 9.2% for their nonprofit counterparts. Purpose: This study aims to gain insight regarding the driving factors behind the high cash flow performance of large rural for-profit hospitals. Methods: Using 3 annual…

Flow regime, temperature, and biotic interactions drive differential declines of trout species under climate change [includes Supporting Information

Treesearch

Seth J. Wenger; Daniel J. Isaak; Charlie Luce; Helen M. Neville; Kurt D. Fausch; Jason B. Dunham; Daniel C. Dauwalter; Michael K. Young; Marketa M. Elsner; Bruce E. Rieman; Alan F. Hamlet; Jack E. Williams

2011-01-01

Broad-scale studies of climate change effects on freshwater species have focused mainly on temperature, ignoring critical drivers such as flow regime and biotic interactions. We use downscaled outputs from general circulation models coupled with a hydrologic model to forecast the effects of altered flows and increased temperatures on four interacting species of trout...

Energy conversion approaches and materials for high-efficiency photovoltaics.

PubMed

Green, Martin A; Bremner, Stephen P

2016-12-20

The past five years have seen significant cost reductions in photovoltaics and a correspondingly strong increase in uptake, with photovoltaics now positioned to provide one of the lowest-cost options for future electricity generation. What is becoming clear as the industry develops is that area-related costs, such as costs of encapsulation and field-installation, are increasingly important components of the total costs of photovoltaic electricity generation, with this trend expected to continue. Improved energy-conversion efficiency directly reduces such costs, with increased manufacturing volume likely to drive down the additional costs associated with implementing higher efficiencies. This suggests the industry will evolve beyond the standard single-junction solar cells that currently dominate commercial production, where energy-conversion efficiencies are fundamentally constrained by Shockley-Queisser limits to practical values below 30%. This Review assesses the overall prospects for a range of approaches that can potentially exceed these limits, based on ultimate efficiency prospects, material requirements and developmental outlook.

Method of achieving ultra-wideband true-time-delay beam steering for active electronically scanned arrays

DOEpatents

Loui, Hung; Brock, Billy C.

2016-10-25

The various embodiments presented herein relate to beam steering an array antenna by modifying intermediate frequency (IF) waveforms prior to conversion to RF signals. For each channel, a direct digital synthesis (DDS) component can be utilized to generate a waveform or modify amplitude, timing and phase of a waveform relative to another waveform, whereby the generation/modification can be performed prior to the IF input port of a mixer on each channel. A local oscillator (LO) signal can be utilized to commonly drive each of the mixers. After conversion at the RF output port of each of the mixers, each RF signal can be transmitted by a respective antenna element in the antenna array. Initiation of transmission of each RF signal can be performed simultaneously at each antenna. The process can be reversed during receive whereby timing, amplitude, and phase of the received can be modified digitally post ADC conversion.

Genetic recombination as a major cause of mutagenesis in the human globin gene clusters.

PubMed

Borg, Joseph; Georgitsi, Marianthi; Aleporou-Marinou, Vassiliki; Kollia, Panagoula; Patrinos, George P

2009-12-01

Homologous recombination is a frequent phenomenon in multigene families and as such it occurs several times in both the alpha- and beta-like globin gene families. In numerous occasions, genetic recombination has been previously implicated as a major mechanism that drives mutagenesis in the human globin gene clusters, either in the form of unequal crossover or gene conversion. Unequal crossover results in the increase or decrease of the human globin gene copies, accompanied in the majority of cases with minor phenotypic consequences, while gene conversion contributes either to maintaining sequence homogeneity or generating sequence diversity. The role of genetic recombination, particularly gene conversion in the evolution of the human globin gene families has been discussed elsewhere. Here, we summarize our current knowledge and review existing experimental evidence outlining the role of genetic recombination in the mutagenic process in the human globin gene families.

Energy dissipation in the blade tip region of an axial fan

NASA Astrophysics Data System (ADS)

Bizjan, B.; Milavec, M.; Širok, B.; Trenc, F.; Hočevar, M.

2016-11-01

A study of velocity and pressure fluctuations in the tip clearance flow of an axial fan is presented in this paper. Two different rotor blade tip designs were investigated: the standard one with straight blade tips and the modified one with swept-back tip winglets. Comparison of integral sound parameters indicates a significant noise level reduction for the modified blade tip design. To study the underlying mechanisms of the energy conversion and noise generation, a novel experimental method based on simultaneous measurements of local flow velocity and pressure has also been developed and is presented here. The method is based on the phase space analysis by the use of attractors, which enable more accurate identification and determination of the local flow structures and turbulent flow properties. Specific gap flow energy derived from the pressure and velocity time series was introduced as an additional attractor parameter to assess the flow energy distribution and dissipation within the phase space, and thus determines characteristic sources of the fan acoustic emission. The attractors reveal a more efficient conversion of the pressure to kinetic flow energy in the case of the modified (tip winglet) fan blade design, and also a reduction in emitted noise levels. The findings of the attractor analysis are in a good agreement with integral fan characteristics (efficiency and noise level), while offering a much more accurate and detailed representation of gap flow phenomena.

Continuous scanning of the mobility and size distribution of charged clusters and nanometer particles in atmospheric air and the Balanced Scanning Mobility Analyzer BSMA

NASA Astrophysics Data System (ADS)

Tammet, H.

2006-12-01

Measuring of charged nanometer particles in atmospheric air is a routine task in research on atmospheric electricity, where these particles are called the atmospheric ions. An aspiration condenser is the most popular instrument for measuring atmospheric ions. Continuous scanning of a mobility distribution is possible when the aspiration condenser is connected as an arm of a balanced bridge. Transfer function of an aspiration condenser is calculated according to the measurements of geometric dimensions, air flow rate, driving voltage, and electric current. The most complicated phase of the calibration is the estimation of the inlet loss of ions due to the Brownian deposition. The available models of ion deposition on the protective inlet screen and the inlet control electrofilter have the uncertainty of about 20%. To keep the uncertainty of measurements low the adsorption should not exceed a few tens of percent. The online conversion of the mobility distribution to the size distribution and a correct reduction of inlet losses are possible when air temperature and pressure are measured simultaneously with the mobility distribution. Two instruments called the Balanced Scanning Mobility Analyzers (BSMA) were manufactured and tested in routine atmospheric measurements. The concentration of atmospheric ions of the size of about a few nanometers is very low and a high air flow rate is required to collect enough of ion current. The air flow of 52 l/s exceeds the air flow in usual aerosol instruments by 2-3 orders of magnitude. The high flow rate reduces the time of ion passage to 60 ms and the heating of air in an analyzer to 0.2 K, which suppresses a possible transformation of ions inside the instrument. The mobility range of the BSMA of 0.032-3.2 cm 2 V - 1 s - 1 is logarithmically uniformly divided into 16 fractions. The size distribution is presented by 12 fractions in the diameter range of 0.4-7.5 nm. The measurement noise of a fraction concentration is typically about 5 cm - 3 and the time resolution is about 10 min when measuring simultaneously both positive and negative ions in atmospheric air.

Glymphatic solute transport does not require bulk flow

PubMed Central

Asgari, Mahdi; de Zélicourt, Diane; Kurtcuoglu, Vartan

2016-01-01

Observations of fast transport of fluorescent tracers in mouse brains have led to the hypothesis of bulk water flow directed from arterial to venous paravascular spaces (PVS) through the cortical interstitium. At the same time, there is evidence for interstitial solute transport by diffusion rather than by directed bulk fluid motion. It has been shown that the two views may be consolidated by intracellular water flow through astrocyte networks combined with mainly diffusive extracellular transport of solutes. This requires the presence of a driving force that has not been determined to date, but for which arterial pulsation has been suggested as the origin. Here we show that arterial pulsation caused by pulse wave propagation is an unlikely origin of this hypothetical driving force. However, we further show that such pulsation may still lead to fast para-arterial solute transport through dispersion, that is, through the combined effect of local mixing and diffusion in the para-arterial space. PMID:27929105

Low energy high pressure miniature screw valve

DOEpatents

Fischer, Gary J [Sandia Park, NM; Spletzer, Barry L [Albuquerque, NM

2006-12-12

A low energy high pressure screw valve having a valve body having an upper portion and a lower portion, said lower portion of said valve body defining an inlet flow passage and an outlet flow passage traversing said valve body to a valve seat, said upper portion of said valve body defining a cavity at said valve seat, a diaphragm restricting flow between said upper portion of said valve body and said lower portion, said diaphragm capable of engaging said valve seat to restrict fluid communication between said inlet passage and said outlet passage, a plunger within said cavity supporting said diaphragm, said plunger being capable of engaging said diaphragm with said valve seat at said inlet and outlet fluid passages, said plunger being in point contact with a drive screw having threads engaged with opposing threads within said upper portion of said valve body such engagement allowing motion of said drive screw within said valve body.

Energy conservation strategy in Hydraulic Power Packs using Variable Frequency Drive IOP Conference Series: Materials Science and Engineering

NASA Astrophysics Data System (ADS)

Ramesh, S.; Ashok, S. Denis; Nagaraj, Shanmukha; Reddy, M. Lohith Kumar; Naulakha, Niranjan Kumar; Adithyakumar, C. R.

2018-02-01

At present, energy consumption is to such an extent that if the same trend goes on then in the future at some point of time, the energy sources will all be exploited. Energy conservation in a hydraulic power pack refers to the reduction in the energy consumed by the power pack. Many experiments have been conducted to reduce the energy consumption and one of those methods is by introducing a variable frequency drive. The main objective of the present work is to reduce the energy consumed by the hydraulic power pack using variable frequency drive. Variable Frequency drive is used to vary the speed of the motor by receiving electrical signals from the pressure switch which acts as the feedback system. Using this concept, the speed of the motor can be varied between the specified limits. In the present work, a basic hydraulic power pack and a variable frequency drive based hydraulic power pack were designed and compared both of them with the results obtained. The comparison was based on the power consumed, rise in temperature, noise levels, and flow of oil through pressure relief valve, total oil flow during loading cycle. By comparing both the circuits, it is found that for the proposed system, consumption of power reduces by 78.4% and is as powerful as the present system.

Influence of driving cycles on unit emissions from passenger cars

NASA Astrophysics Data System (ADS)

Joumard, R.; André, M.; Vidon, R.; Tassel, P.; Pruvost, C.

Small samples of petrol engine or diesel cars, equipped with or without catalysts, were tested over 36 driving cycles divided into four categories - standard cycles and three sets of cycles more representative of real-world driving conditions. The tests addressed standard gaseous pollutants and fuel consumption and also less frequently measured pollutant such as CH 4. In the first part of this paper we examine cold emissions in order to assess the duration of the cold start impact and the representativity of the cold ECE15 cycle. Then unit emissions are compared over the four driving cycle families. As compared to representative cycles, the standardised cycles underestimate hot emissions by almost 50% for petrol engine cars and 30% for diesel vehicles. Conversely, the results obtained for the three representative cycle families are in relatively close agreement with each other - within approximately 10%. However, the cinematic properties of the three families differ. Finally, we demonstrate that weighting all emission data equally, not taking into account the weight of each cycle in overall traffic, introduces significant biases, particularly when plotting emission vs. average speed curves.

Conversion of the trace elements Zn, Cd, and Pb in the combustion of near-Moscow coals

DOE Office of Scientific and Technical Information (OSTI.GOV)

E.V. Samuilov; L.N. Lebedeva; L.S. Pokrovskaya

A model for the conversion of trace elements in the combustion of near-Moscow coals based on a complex approach combining the capabilities of geochemistry, chemical thermodynamics, phase analysis, and chemical kinetics is proposed. The conversion of the trace elements Zn, Cd, and Pb as the constituents of near-Moscow coal in the flow of coal combustion products along the line of the P-59 boiler at the Ryazanskaya Thermal Power Plant was calculated. Experimental data were used in the development of the model and in calculations.

Simulation of aerodynamic noise and vibration noise in hard disk drives

NASA Astrophysics Data System (ADS)

Zhu, Lei; Shen, Sheng-Nan; Li, Hui; Zhang, Guo-Qing; Cui, Fu-Hao

2018-05-01

Internal flow field characteristics of HDDs are usually influenced by the arm swing during seek operations. This, in turn, can affect aerodynamic noise and airflow-induced noise. In this paper, the dynamic mesh method is used to calculate the flow-induced vibration (FIV) by transient structure analysis and the boundary element method (BEM) is utilized to predict the vibration noise. Two operational states are considered: the arm is fixed and swinging over the disk. Both aerodynamic noise and vibration noise inside drives increase rapidly with increase in disk rotation and arm swing velocities. The largest aerodynamic noise source is always located near the arm and swung with the arm.

Continuous Flow Aerobic Alcohol Oxidation Reactions Using a Heterogeneous Ru(OH)x/Al2O3 Catalyst

PubMed Central

2015-01-01

Ru(OH)x/Al2O3 is among the more versatile catalysts for aerobic alcohol oxidation and dehydrogenation of nitrogen heterocycles. Here, we describe the translation of batch reactions to a continuous-flow method that enables high steady-state conversion and single-pass yields in the oxidation of benzylic alcohols and dehydrogenation of indoline. A dilute source of O2 (8% in N2) was used to ensure that the reaction mixture, which employs toluene as the solvent, is nonflammable throughout the process. A packed bed reactor was operated isothermally in an up-flow orientation, allowing good liquid–solid contact. Deactivation of the catalyst during the reaction was modeled empirically, and this model was used to achieve high conversion and yield during extended operation in the aerobic oxidation of 2-thiophene methanol (99+% continuous yield over 72 h). PMID:25620869

The in situ generation and reactive quench of diazonium compounds in the synthesis of azo compounds in microreactors

PubMed Central

Akwi, Faith M

2016-01-01

Summary In this paper, a micro-fluidic optimized process for the continuous flow synthesis of azo compounds is presented. The continuous flow synthesis of Sudan II azo dye was used as a model reaction for the study. At found optimal azo coupling reaction temperature and pH an investigation of the optimum flow rates of the reactants for the diazotization and azo coupling reactions in Little Things Factory-MS microreactors was performed. A conversion of 98% was achieved in approximately 2.4 minutes and a small library of azo compounds was thus generated under these reaction conditions from couplers with aminated or hydroxylated aromatic systems. The scaled up synthesis of these compounds in PTFE tubing (i.d. 1.5 mm) was also investigated, where good reaction conversions ranging between 66–91% were attained. PMID:27829903

Free Association in Sex Education: Understanding Sexuality as the Flow of Thought in Conversation and Curriculum

ERIC Educational Resources Information Center

Casemore, Brian

2010-01-01

This paper draws on the theory and method of free association in psychoanalysis to frame an investigation of the content, structure, and function of the thinking expressed in conversations about sexuality and sexual health. The investigation emerges from an ongoing three-year study of the way adolescents, teachers, and peer sex educators negotiate…

How plasmas dissipate: cascade and the production of internal energy and entropy in weakly collisional plasma turbulence

NASA Astrophysics Data System (ADS)

Matthaeus, W. H.; Yang, Y.; Servidio, S.; Parashar, T.; Chasapis, A.; Roytershteyn, V.

2017-12-01

Turbulence cascade transfers energy from large scale to small scale but what happens once kinetic scales are reached? In a collisional medium, viscosity and resistivity remove fluctuation energy in favor of heat. In the weakly collisional solar wind, (or corona, m-sheath, etc.), the sequence of events must be different. Heating occurs, but through what mechanisms? In standard approaches, dissipation occurs though linear wave modes or instabilities and one seeks to identify them. A complementary view is that cascade leads to several channels of energy conversion, interchange and spatial rearrangement that collectively leads to production of internal energy. Channels may be described using compressible MHD & multispecies Vlasov Maxwell formulations. Key steps are: Conservative rearrangement of energy in space; Parallel incompressible and compressible cascades - conservative rearrangment in scale; electromagnetic work on particles that drives flows, both macroscopic and microscopic; and pressure-stress interactions, both compressive and shear-like, that produces internal energy. Examples given from MHD, PIC simulations and MMS observations. A more subtle issue is how entropy is related to this degeneration (or, "dissipation") of macroscopic, fluid-scale fluctuations. We discuss this in terms of Boltzmann and thermodynamic entropies, and velocity space effects of collisions.

Expiratory timing in obstructive sleep apnoeas.

PubMed

Cibella, F; Marrone, O; Sanci, S; Bellia, V; Bonsignore, G

1990-03-01

Diaphragmatic electromyogram was recorded during NREM sleep in 4 patients affected by obstructive sleep apnoea (OSA) syndrome in order to evaluate the behaviour of expiratory time (TE) in the course of the obstructive apnoea-ventilation cycle. The two components of TE, i.e. time of post-inspiratory inspiratory activity (TPIIA) and time of expiratory phase 2 (TE2) were separately analysed. TPIIA showed a short duration, with only minor variations, within the apnoea, while its duration was more variable and longer in the interapnoeic periods: the longest TPIIA values were associated with the highest inspiratory volumes in the same breaths. This behaviour seemed regulated according to the need of a more or less effective expiratory flow braking, probably as a result of pulmonary stretch receptors discharge. Conversely TE2 showed a continuous gradual modulation, progressively increasing in the pre-apnoeic period, decreasing during the apnoea and increasing in the post-apnoeic period: these TE2 variations seemed related to oscillations in chemical drive. These data show that TE in the obstructive apnoea-ventilation cycle results from a different modulation in its two components and suggest that both mechanical and chemical influences play a role in its overall duration.

NDCX-II target experiments and simulations

DOE PAGES

Barnard, J. J.; More, R. M.; Terry, M.; ...

2013-06-13

The ion accelerator NDCX-II is undergoing commissioning at Lawrence Berkeley National Laboratory (LBNL). Its principal mission is to explore ion-driven High Energy Density Physics (HEDP) relevant to Inertial Fusion Energy (IFE) especially in the Warm Dense Matter (WDM) regime. We have carried out hydrodynamic simulations of beam-heated targets for parameters expected for the initial configuration of NDCX-II. For metal foils of order one micron thick (thin targets), the beam is predicted to heat the target in a timescale comparable to the hydrodynamic expansion time for experiments that infer material properties from measurements of the resulting rarefaction wave. We have alsomore » carried out hydrodynamic simulations of beam heating of metallic foam targets several tens of microns thick (thick targets) in which the ion range is shorter than the areal density of the material. In this case shock waves will form and we derive simple scaling laws for the efficiency of conversion of ion energy into kinetic energy of fluid flow. Geometries with a tamping layer may also be used to study the merging of a tamper shock with the end-of-range shock. As a result, this process can occur in tamped, direct drive IFE targets.« less

A Comparison of Martian Transient Wave Energetics in High and Low Optical Depth Environments

NASA Astrophysics Data System (ADS)

Battalio, J. M.; Szunyogh, I.; Lemmon, M. T.

2016-12-01

The local energetics of individual transient eddies from the Mars Analysis Correction Data Assimilation (MACDA) is compared between a year with a global-scale dust storm (MY 25) and two years of relatively low optical depth conditions. Eddies in each year are considered from a period of strong wave activity in the northern hemisphere before the winter solstice (Ls=170-240°). The local growth of eddies is typically triggered by geopotential flux convergence. While all waves exhibit some baroclinic growth, baroclinic energy conversion is weaker in the waves that occur during the global-scale dust storm. The weaker baroclinic energy conversion in these waves, however, is compensated by a more intense barotropic transfer of the kinetic energy from the mean flow to the waves: the contribution from barotropic energy conversion allows eddies during the global-scale dust storm to attain roughly the same maximum eddy kinetic energy as eddies during the low optical depth years. Individual eddies in the waves decay through a combination of barotropic conversion of the kinetic energy from the waves to the mean flow, geopotential flux divergence, and dissipation in both the high- and the low-optical-depth years.

Conversion to Silodosin in Men on Conventional α1 -Blockers for Symptomatic Benign Prostatic Hyperplasia.

PubMed

Tanaka, Masahiko; Niimi, Aya; Tomita, Kyoichi; Homma, Yukio

2010-04-01

α1 -blockers have commonly been used as first-line medical therapy for symptomatic benign prostatic hyperplasia (BPH). Recently, a highly selective α1A -adrenoceptor antagonist, silodosin, was developed in Japan. We examined the efficacy and safety of conversion from conventional α1 -blockers to silodosin in men with BPH. Conversion to silodosin was proposed to consecutive patients on conventional α1 -blockers for symptomatic BPH for at least 6 months. The effects of conversion were examined by the International Prostate Symptom Score, quality of life index, overactive bladder symptom score, peak flow rate, residual urine volume, and adverse events at 12 weeks. The efficacy of silodosin was also evaluated by patients' impression. Eighty-one men underwent conversion, for the most part because of dissatisfaction with the efficacy of their current treatment in improving nocturia or weak stream. The International Prostate Symptom Score total score significantly improved from 12.7 ± 5.9 at baseline to 10.6 ± 5.4 at 4 weeks (P < 0.001) and 10.9 ± 5.8 at 12 weeks (P < 0.01). The progress was mostly due to improvement in voiding symptoms, although reduction of storage symptoms was also significant. The quality of life index also significantly decreased with conversion to silodosin. Efficacy as judged by patients' impression was 76% (37/49) at 12 weeks of treatment. None of the overactive bladder symptom score, peak flow rate, and residual urine volume exhibited significant change. No serious adverse events were observed during the study period. Conversion to silodosin may be beneficial in men who are dissatisfied with conventional α1 -blockers for BPH, and be particularly useful in improving voiding symptoms. © 2010 Blackwell Publishing Asia Pty Ltd.

Amelioration de la qualite d'energie d'un systeme de conversion d'energie eolienne a base de machine asynchrone a double alimentation et connecte au reseau electrique =

NASA Astrophysics Data System (ADS)

Abderrahim, Iheb

Wind power generation has grown strongly in the last decade. This results in the development of Wind Energy Conversion System WECS at the levels of modeling and electrical control. Modern WECS operate at varying wind speeds and are equipped with synchronous and asynchronous generators. Among these generators, the Doubly-Fed Induction Generator (DFIG) offers several advantages and capabilities of active and reactive power in four quadrants. WECS based DFIG also causes less conversion costs and minimum energy losses compared with a WECS based on a synchronous generator powered entirely by full scale of power converters. The connection of such a system to the electrical distribution network involves bidirectional operation of networks. This is clearly established in sub and super synchronous operating modes of DFIG. The grid provides the active power to the rotor of DFIG in sub synchronous operating mode and receives the active power of the rotor in super synchronous operating mode of DFIG. Energy quality is thus of major importance during the integration of wind power to the grid. Poor wave quality can affect network stability and could even cause major problems and consequences. This is even more critical where non-linear loads such as the switching power supplies and variable speed drives, are connected to the grid. The idea of this research work is how to mitigate the problems associated with the wave quality while ensuring better implementation of DFIG so that the whole of WECS remains insensitive to external disturbances and parametric variations. The Grid Side Converter (GSC) must be able to compensate harmonics, current unbalance and reactive power injected by a nonlinear three-phase unbalanced load connected to the grid. In addition to these innovative features to improve the conditions of operation of the grid, it provides also the power flow during different modes of operation of the DFIG. It is considered a simple, efficient and cost competitive solution by saving the use of other power equipment. At the same time, the energy efficiency of wind power conversion chain should be improved by extracting the MPPT. Searching allows us to select vector control and control in synchronous reference to achieve these objectives. WECS based DFIG is simulated in MATLAB SIMULINK in the presence of a non-linear balanced and unbalanced three-phase load.

Mental workload while driving: effects on visual search, discrimination, and decision making.

PubMed

Recarte, Miguel A; Nunes, Luis M

2003-06-01

The effects of mental workload on visual search and decision making were studied in real traffic conditions with 12 participants who drove an instrumented car. Mental workload was manipulated by having participants perform several mental tasks while driving. A simultaneous visual-detection and discrimination test was used as performance criteria. Mental tasks produced spatial gaze concentration and visual-detection impairment, although no tunnel vision occurred. According to ocular behavior analysis, this impairment was due to late detection and poor identification more than to response selection. Verbal acquisition tasks were innocuous compared with production tasks, and complex conversations, whether by phone or with a passenger, are dangerous for road safety.

Is Accreditation Accountable? The Continuing Conversation between Accreditation and the Federal Government. CHEA Monograph Series 2003, Number 1

ERIC Educational Resources Information Center

Eaton, Judith S.

2003-01-01

This monograph addresses key issues in the current discussion between accreditation and the federal government relative to accountability and higher education. The reauthorization of the Higher Education Act (HEA) now being discussed in Congress is driving this issue to the top of the academic agenda. The paper describes some of the accountability…

Pushing for the "Sputnik Moment": A Conversation with Arizona Governor and National Governor's Association Chair, Janet Napolitano

ERIC Educational Resources Information Center

McLester, Susan

2007-01-01

Janet Napolitano is the governor of Arizona and chair of the National Governor's Association. Napolitano, a Democrat, has brought a new energy to her state and to the nation with initiatives that demonstrate the fact that she really means business. Topping the list is Innovation America, which aims to drive American competitiveness via government…

Current CRISPR gene drive systems are likely to be highly invasive in wild populations.

PubMed

Noble, Charleston; Adlam, Ben; Church, George M; Esvelt, Kevin M; Nowak, Martin A

2018-06-19

Recent reports have suggested that self-propagating CRISPR-based gene drive systems are unlikely to efficiently invade wild populations due to drive-resistant alleles that prevent cutting. Here we develop mathematical models based on existing empirical data to explicitly test this assumption for population alteration drives. Our models show that although resistance prevents spread to fixation in large populations, even the least effective drive systems reported to date are likely to be highly invasive. Releasing a small number of organisms will often cause invasion of the local population, followed by invasion of additional populations connected by very low rates of gene flow. Hence, initiating contained field trials as tentatively endorsed by the National Academies report on gene drive could potentially result in unintended spread to additional populations. Our mathematical results suggest that self-propagating gene drive is best suited to applications such as malaria prevention that seek to affect all wild populations of the target species. © 2018, Noble et al.

High Explosive Detonation-Confiner Interactions

NASA Astrophysics Data System (ADS)

Short, Mark; Quirk, James J.

2018-01-01

The primary purpose of a detonation in a high explosive (HE) is to provide the energy to drive a surrounding confiner, typically for mining or munitions applications. The details of the interaction between an HE detonation and its confinement are essential to achieving the objectives of the explosive device. For the high pressures induced by detonation loading, both the solid HE and confiner materials will flow. The structure and speed of a propagating detonation, and ultimately the pressures generated in the reaction zone to drive the confiner, depend on the induced flow both within the confiner and along the HE-confiner material interface. The detonation-confiner interactions are heavily influenced by the material properties and, in some cases, the thickness of the confiner. This review discusses the use of oblique shock polar analysis as a means of characterizing the possible range of detonation-confiner interactions. Computations that reveal the fluid mechanics of HE detonation-confiner interactions for finite reaction-zone length detonations are discussed and compared with the polar analysis. This includes cases of supersonic confiner flow; subsonic, shock-driven confiner flow; subsonic, but shockless confiner flow; and sonic flow at the intersection of the detonation shock and confiner material interface. We also summarize recent developments, including the effects of geometry and porous material confinement, on detonation-confiner interactions.

Active Listening Delays Attentional Disengagement and Saccadic Eye Movements.

PubMed

Lester, Benjamin D; Vecera, Shaun P

2018-06-01

Successful goal-directed visual behavior depends on efficient disengagement of attention. Attention must be withdrawn from its current focus before being redeployed to a new object or internal process. Previous research has demonstrated that occupying cognitive processes with a secondary cellular phone conversation impairs attentional functioning and driving behavior. For example, attentional processing is significantly impacted by concurrent cell phone use, resulting in decreased explicit memory for on-road information. Here, we examined the impact of a critical component of cell-phone use-active listening-on the effectiveness of attentional disengagement. In the gap task-a saccadic manipulation of attentional disengagement-we measured saccade latencies while participants performed a secondary active listening task. Saccadic latencies significantly increased under an active listening load only when attention needed to be disengaged, indicating that active listening delays a disengagement operation. Simple dual-task interference did not account for the observed results. Rather, active cognitive engagement is required for measurable disengagement slowing to be observed. These results have implications for investigations of attention, gaze behavior, and distracted driving. Secondary tasks such as active listening or cell-phone conversations can have wide-ranging impacts on cognitive functioning, potentially impairing relatively elementary operations of attentional function, including disengagement.

Investigation of the cylindrical vacuum hohlraum energy in the first implosion experiment at the SGIII laser facility

NASA Astrophysics Data System (ADS)

Zhang, Huasen; Jiang, Wei; Ge, Fengjun; Song, Peng; Zou, Shiyang; Huang, Tianxuan; Li, Sanwei; Yang, Dong; Li, Zhichao; Hou, Lifei; Guo, Liang; Che, Xingsen; Du, Huabing; Xie, Xufei; He, Xiaoan; Li, Chaoguang; Zha, Weiyi; Xu, Tao; Liu, Yonggang; Wei, Huiyue; Liu, Xiangming; Chen, Zhongjing; Zhang, Xing; Yan, Ji; Pu, Yudong; Peng, Xiaoshi; Li, Yulong; Gu, Peijun; Zheng, Wudi; Liu, Jie; Ding, Yongkun; Zhu, Shaoping

2018-02-01

The cylindrical vacuum hohlraum energy at the SGIII laser facility [X. T. He and W. Y. Zhang, Eur. Phys. J. D 44, 227 (2007) and W. Zheng et al., High Power Laser Sci. Eng. 4, e21 (2016)] is investigated for the first time. The hohlraum size and the laser energy are intermediate between the Nova and NIF typical hohlraum experiments. It is found that the SGIII hohlraum exhibits an x-ray conversion efficiency of about 85%, which is more close to that of the NIF hohlraum. The LARED simulations of the SGIII hohlraum underestimate about 15% of the radiation flux measured from the laser entrance hole, while the capsule radiation drive inferred from the x-ray bangtime is roughly consistent with the experiments. The underestimation of the SGIII hohlraum radiation flux is mainly caused by the more enclosed laser entrance hole in the LARED simulation. The comparison between the SGIII and NIF hohlraum simulations by LARED indicates that the LARED generally underestimates the measured radiation flux by 15% for the high x-ray conversion efficiency hohlraums, while it can roughly predict the capsule radiation drive inside the hohlraum.

Quantum modeling of ultrafast photoinduced charge separation

NASA Astrophysics Data System (ADS)

Rozzi, Carlo Andrea; Troiani, Filippo; Tavernelli, Ivano

2018-01-01

Phenomena involving electron transfer are ubiquitous in nature, photosynthesis and enzymes or protein activity being prominent examples. Their deep understanding thus represents a mandatory scientific goal. Moreover, controlling the separation of photogenerated charges is a crucial prerequisite in many applicative contexts, including quantum electronics, photo-electrochemical water splitting, photocatalytic dye degradation, and energy conversion. In particular, photoinduced charge separation is the pivotal step driving the storage of sun light into electrical or chemical energy. If properly mastered, these processes may also allow us to achieve a better command of information storage at the nanoscale, as required for the development of molecular electronics, optical switching, or quantum technologies, amongst others. In this Topical Review we survey recent progress in the understanding of ultrafast charge separation from photoexcited states. We report the state-of-the-art of the observation and theoretical description of charge separation phenomena in the ultrafast regime mainly focusing on molecular- and nano-sized solar energy conversion systems. In particular, we examine different proposed mechanisms driving ultrafast charge dynamics, with particular regard to the role of quantum coherence and electron-nuclear coupling, and link experimental observations to theoretical approaches based either on model Hamiltonians or on first principles simulations.

Parametric Study of Reactive Melt Infiltration

NASA Technical Reports Server (NTRS)

Nelson, Emily S.; Colella, Phillip

2000-01-01

Reactive melt infiltration is viewed as a promising means of achieving near-net shape manufacturing with quick processing time and at low cost. Since the reactants and products are, in general, of varying density, overall conservation of mass dictates that there is a force related to chemical conversion which can directly influence infiltration behavior. In effect, the driving pressure forces may compete with the forces from chemical conversion, affecting the advancement of the front. We have developed a two-dimensional numerical code to examine these effects, using reaction-formed silicon carbide as a model system for this process. We have examined a range of initial porosities, pore radii, and reaction rates in order to investigate their effects on infiltration dynamics.

Risk factors of mobile phone use while driving in Queensland: Prevalence, attitudes, crash risk perception, and task-management strategies.

PubMed

Oviedo-Trespalacios, Oscar; King, Mark; Haque, Md Mazharul; Washington, Simon

2017-01-01

Distracted driving is one of the most significant human factor issues in transport safety. Mobile phone interactions while driving may involve a multitude of cognitive and physical resources that result in inferior driving performance and reduced safety margins. The current study investigates characteristics of usage, risk factors, compensatory strategies in use and characteristics of high-frequency offenders of mobile phone use while driving. A series of questions were administered to drivers in Queensland (Australia) using an on-line questionnaire. A total of 484 drivers (34.9% males and 49.8% aged 17-25) participated anonymously. At least one of every two motorists surveyed reported engaging in distracted driving. Drivers were unable to acknowledge the increased crash risk associated with answering and locating a ringing phone in contrast to other tasks such as texting/browsing. Attitudes towards mobile phone usage were more favourable for talking than texting or browsing. Lowering the driving speed and increasing the distance from the vehicle in front were the most popular task-management strategies for talking and texting/browsing while driving. On the other hand, keeping the mobile phone low (e.g. in the driver's lap or on the passenger seat) was the favourite strategy used by drivers to avoid police fines for both talking and texting/browsing. Logistic regression models were fitted to understand differences in risk factors for engaging in mobile phone conversations and browsing/texting while driving. For both tasks, exposure to driving, driving experience, driving history (offences and crashes), and attitudes were significant predictors. Future mobile phone prevention efforts would benefit from development of safe attitudes and increasing risk literacy. Enforcement of mobile phone distraction should be re-engineered, as the use of task-management strategies to evade police enforcement seems to dilute its effect on the prevention of this behaviour. Some countermeasures and suggestions were proposed in the design of public education campaigns and driver-mobile phone interaction.

Risk factors of mobile phone use while driving in Queensland: Prevalence, attitudes, crash risk perception, and task-management strategies

PubMed Central

King, Mark; Haque, Md. Mazharul; Washington, Simon

2017-01-01

Distracted driving is one of the most significant human factor issues in transport safety. Mobile phone interactions while driving may involve a multitude of cognitive and physical resources that result in inferior driving performance and reduced safety margins. The current study investigates characteristics of usage, risk factors, compensatory strategies in use and characteristics of high-frequency offenders of mobile phone use while driving. A series of questions were administered to drivers in Queensland (Australia) using an on-line questionnaire. A total of 484 drivers (34.9% males and 49.8% aged 17–25) participated anonymously. At least one of every two motorists surveyed reported engaging in distracted driving. Drivers were unable to acknowledge the increased crash risk associated with answering and locating a ringing phone in contrast to other tasks such as texting/browsing. Attitudes towards mobile phone usage were more favourable for talking than texting or browsing. Lowering the driving speed and increasing the distance from the vehicle in front were the most popular task-management strategies for talking and texting/browsing while driving. On the other hand, keeping the mobile phone low (e.g. in the driver’s lap or on the passenger seat) was the favourite strategy used by drivers to avoid police fines for both talking and texting/browsing. Logistic regression models were fitted to understand differences in risk factors for engaging in mobile phone conversations and browsing/texting while driving. For both tasks, exposure to driving, driving experience, driving history (offences and crashes), and attitudes were significant predictors. Future mobile phone prevention efforts would benefit from development of safe attitudes and increasing risk literacy. Enforcement of mobile phone distraction should be re-engineered, as the use of task-management strategies to evade police enforcement seems to dilute its effect on the prevention of this behaviour. Some countermeasures and suggestions were proposed in the design of public education campaigns and driver-mobile phone interaction. PMID:28877200

Computational Fluid Dynamics Simulation of Flows in an Oxidation Ditch Driven by a New Surface Aerator.

PubMed

Huang, Weidong; Li, Kun; Wang, Gan; Wang, Yingzhe

2013-11-01

In this article, we present a newly designed inverse umbrella surface aerator, and tested its performance in driving flow of an oxidation ditch. Results show that it has a better performance in driving the oxidation ditch than the original one with higher average velocity and more uniform flow field. We also present a computational fluid dynamics model for predicting the flow field in an oxidation ditch driven by a surface aerator. The improved momentum source term approach to simulate the flow field of the oxidation ditch driven by an inverse umbrella surface aerator was developed and validated through experiments. Four kinds of turbulent models were investigated with the approach, including the standard k - ɛ model, RNG k - ɛ model, realizable k - ɛ model, and Reynolds stress model, and the predicted data were compared with those calculated with the multiple rotating reference frame approach (MRF) and sliding mesh approach (SM). Results of the momentum source term approach are in good agreement with the experimental data, and its prediction accuracy is better than MRF, close to SM. It is also found that the momentum source term approach has lower computational expenses, is simpler to preprocess, and is easier to use.

Fourier-domain study of drift turbulence driven sheared flow in a laboratory plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, M.; Tynan, G. R.; Holland, C.

2010-03-15

Frequency-resolved nonlinear internal and kinetic energy transfer rates have been measured in the Controlled Shear Decorrelation Experiment (CSDX) linear plasma device using a recently developed technique [Xu et al., Phys. Plasmas 16, 042312 (2009)]. The results clearly show a net kinetic energy transfer into the zonal flow frequency region, consistent with previous time-domain observations of turbulence-driven shear flows [Tynan et al., Plasma Phys. Controlled Fusion 48, S51 (2006)]. The experimentally measured dispersion relation has been used to map the frequency-resolved energy transfer rates into the wave number domain, which shows that the shear flow drive comes from midrange (k{sub t}hetarho{submore » S}>0.3) drift fluctuations, and the strongest flow drive comes from k{sub t}hetarho{sub S}approx =1 fluctuations. Linear growth rates have been inferred from a linearized Hasegawa-Wakatani model [Hasegawa et al., Phys. Fluids 22, 2122 (1979)], which indicates that the m=0 mode is linearly stable and the m=1-10 modes (corresponding to k{sub t}hetarho{sub S}>0.3) are linearly unstable for the n=1 and n=2 radial eigenmodes. This is consistent with our energy transfer measurements.« less

Fiber-Optic/Photoelastic Flow Sensors

NASA Technical Reports Server (NTRS)

Wesson, Laurence N.; Cabato, Nellie L.; Brooks, Edward F.

1995-01-01

Simple, rugged, lightweight transducers detect periodic vortices. Fiber-optic-coupled transducers developed to measure flows over wide dynamic ranges and over wide temperature ranges in severe environments. Used to measure flows of fuel in advanced aircraft engines. Feasibility of sensors demonstrated in tests of prototype sensor in water flowing at various temperatures and speeds. Particularly attractive for aircraft applications because optical fibers compact and make possible transmission of sensor signals at high rates with immunity from electromagnetic interference at suboptical frequencies. Sensors utilize optical-to-optical conversion via photoelastic effect.

Associations between motor unit action potential parameters and surface EMG features.

PubMed

Del Vecchio, Alessandro; Negro, Francesco; Felici, Francesco; Farina, Dario

2017-10-01

The surface interference EMG signal provides some information on the neural drive to muscles. However, the association between neural drive to muscle and muscle activation has long been debated with controversial indications due to the unavailability of motor unit population data. In this study, we clarify the potential and limitations of interference EMG analysis to infer motor unit recruitment strategies with an experimental investigation of several concurrently active motor units and of the associated features of the surface EMG. For this purpose, we recorded high-density surface EMG signals during linearly increasing force contractions of the tibialis anterior muscle, up to 70% of maximal force. The recruitment threshold (RT), conduction velocity (MUCV), median frequency (MDF MU ), and amplitude (RMS MU ) of action potentials of 587 motor units from 13 individuals were assessed and associated with features of the interference EMG. MUCV was positively associated with RT ( R 2 = 0.64 ± 0.14), whereas MDF MU and RMS MU showed a weaker relation with RT ( R 2 = 0.11 ± 0.11 and 0.39 ± 0.24, respectively). Moreover, the changes in average conduction velocity estimated from the interference EMG predicted well the changes in MUCV ( R 2 = 0.71), with a strong association to ankle dorsiflexion force ( R 2 = 0.81 ± 0.12). Conversely, both the average EMG MDF and RMS were poorly associated with motor unit recruitment. These results clarify the limitations of EMG spectral and amplitude analysis in inferring the neural strategies of muscle control and indicate that, conversely, the average conduction velocity could provide relevant information on these strategies. NEW & NOTEWORTHY The surface EMG provides information on the neural drive to muscles. However, the associations between EMG features and neural drive have been long debated due to unavailability of motor unit population data. Here, by using novel highly accurate decomposition of the EMG, we related motor unit population behavior to a wide range of voluntary forces. The results fully clarify the potential and limitation of the surface EMG to provide estimates of the neural drive to muscles. Copyright © 2017 the American Physiological Society.

Conversion of a wet waste feedstock to biocrude by hydrothermal processing in a continuous-flow reactor: grape pomace

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elliott, Douglas C.; Schmidt, Andrew J.; Hart, Todd R.

Wet waste feedstocks present an apt opportunity for biomass conversion to fuels by hydrothermal processing. In this study, grape pomace slurries from two varieties, Montepulciano and cabernet sauvignon, have been converted into a biocrude by hydrothermal liquefaction (HTL) in a bench-scale, continuous-flow reactor system. Carbon conversion to gravity-separable biocrude product up to 56 % was accomplished at relatively low temperature (350 C) in a pressurized (sub-critical liquid water) environment (20 MPa) when using grape pomace feedstock slurry with a 16.8 wt% concentration of dry solids processed at a liquid hourly space velocity of 2.1 h-1. Direct oil recovery was achievedmore » without the use of a solvent and biomass trace mineral components were removed by processing steps so that they did not cause processing difficulties. In addition, catalytic hydrothermal gasification (CHG) was effectively applied for HTL byproduct water cleanup using a Ru on C catalyst in a fixed bed producing a gas composed of methane and carbon dioxide from water soluble organics. Conversion of 99.8% of the chemical oxygen demand (COD) left in the aqueous phase was demonstrated. As a result, high conversion of grape pomace to liquid and gas fuel products was found with residual organic contamination in byproduct water reduced to <150 mg/kg COD.« less

Methods and apparatus for using gas and liquid phase cathodic depolarizers

NASA Technical Reports Server (NTRS)

Murphy, Oliver J. (Inventor); Hitchens, G. Duncan (Inventor)

1998-01-01

The invention provides methods for using gas and liquid phase cathodic depolarizers in an electrochemical cell having a cation exchange membrane in intimate contact with the anode and cathode. The electrochemical conversion of cathodic depolarizers at the cathode lowers the cell potential necessary to achieve a desired electrochemical conversion, such as ozone evolution, at the anode. When gaseous cathodic depolarizers, such as oxygen, are used, a gas diffusion cathode having the cation exchange membrane bonded thereto is preferred. When liquid phase cathodic depolarizers are used, the cathode may be a flow-by electrode, flow-through electrode, packed-bed electrode or a fluidized-bed electrode in intimate contact with the cation exchange membrane.

Conversion of blackbody radiation into laser energy

NASA Technical Reports Server (NTRS)

Mcinville, R. M.; Hassan, H. A.

1982-01-01

By employing detailed kinetic models, three concepts which utilize a blackbody cavity for the conversion of solar energy into laser energy using a CO2 lasant are analyzed and compared. In the first, the blackbody radiation is used to excite flowing CO2 directly. The second and third employ a mixing laser concept with CO and N2 being the donor gases. The CO is optically pumped while thermal heating excites the N2. Blackbody temperatures ranging from 1500 deg K - 2500 deg K are considered. Based on calculated laser power output per unit flow rate of CO2, it appears that the N2-CO2 mixing laser is the most attractive system.

Novel Nuclear Powered Photocatalytic Energy Conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

White,John R.; Kinsmen,Douglas; Regan,Thomas M.

2005-08-29

The University of Massachusetts Lowell Radiation Laboratory (UMLRL) is involved in a comprehensive project to investigate a unique radiation sensing and energy conversion technology with applications for in-situ monitoring of spent nuclear fuel (SNF) during cask transport and storage. The technology makes use of the gamma photons emitted from the SNF as an inherent power source for driving a GPS-class transceiver that has the ability to verify the position and contents of the SNF cask. The power conversion process, which converts the gamma photon energy into electrical power, is based on a variation of the successful dye-sensitized solar cell (DSSC)more » design developed by Konarka Technologies, Inc. (KTI). In particular, the focus of the current research is to make direct use of the high-energy gamma photons emitted from SNF, coupled with a scintillator material to convert some of the incident gamma photons into photons having wavelengths within the visible region of the electromagnetic spectrum. The high-energy gammas from the SNF will generate some power directly via Compton scattering and the photoelectric effect, and the generated visible photons output from the scintillator material can also be converted to electrical power in a manner similar to that of a standard solar cell. Upon successful implementation of an energy conversion device based on this new gammavoltaic principle, this inherent power source could then be utilized within SNF storage casks to drive a tamper-proof, low-power, electronic detection/security monitoring system for the spent fuel. The current project has addressed several aspects associated with this new energy conversion concept, including the development of a base conceptual design for an inherent gamma-induced power conversion unit for SNF monitoring, the characterization of the radiation environment that can be expected within a typical SNF storage system, the initial evaluation of Konarka's base solar cell design, the design and fabrication of a range of new cell materials and geometries at Konarka's manufacturing facilities, and the irradiation testing and evaluation of these new cell designs within the UML Radiation Laboratory. The primary focus of all this work was to establish the proof of concept of the basic gammavoltaic principle using a new class of dye-sensitized photon converter (DSPC) materials based on KTI's original DSSC design. In achieving this goal, this report clearly establishes the viability of the basic gammavoltaic energy conversion concept, yet it also identifies a set of challenges that must be met for practical implementation of this new technology.« less

Computational fluid dynamics (CFD) in the design of a water-jet-drive system

NASA Technical Reports Server (NTRS)

Garcia, Roberto

1994-01-01

NASA/Marshall Space Flight Center (MSFC) has an ongoing effort to transfer to industry the technologies developed at MSFC for rocket propulsion systems. The Technology Utilization (TU) Office at MSFC promotes these efforts and accepts requests for assistance from industry. One such solicitation involves a request from North American Marine Jet, Inc. (NAMJ) for assistance in the design of a water-jet-drive system to fill a gap in NAMJ's product line. NAMJ provided MSFC with a baseline axial flow impeller design as well as the relevant working parameters (rpm, flow rate, etc.). This baseline design was analyzed using CFD, and significant deficiencies identified. Four additional analyses were performed involving MSFC changes to the geometric and operational parameters of the baseline case. Subsequently, the impeller was redesigned by NAMJ and analyzed by MSFC. This new configuration performs significantly better than the baseline design. Similar cooperative activities are planned for the design of the jet-drive inlet.

Magnetic energy flow in the solar wind.

NASA Technical Reports Server (NTRS)

Modisette, J. L.

1972-01-01

Discussion of the effect of rotation (tangential flow) of the solar wind on the conclusions of Whang (1971) suggesting an increase in the solar wind velocity due to the conversion of magnetic energy to kinetic energy. It is shown that the effect of the rotation of the sun on the magnetic energy flow results in most of the magnetic energy being transported by magnetic shear stress near the sun.

Numerical and Experimental Investigation of Turbulent Transport Control via Shaping of Radial Plasma Flow Profiles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gilmore, Mark Allen

Turbulence, and turbulence-driven transport are ubiquitous in magnetically confined plasmas, where there is an intimate relationship between turbulence, transport, instability driving mechanisms (such as gradients), plasma flows, and flow shear. Though many of the detailed physics of the interrelationship between turbulence, transport, drive mechanisms, and flow remain unclear, there have been many demonstrations that transport and/or turbulence can be suppressed or reduced via manipulations of plasma flow profiles. This is well known in magnetic fusion plasmas [e.g., high confinement mode (H-mode) and internal transport barriers (ITB’s)], and has also been demonstrated in laboratory plasmas. However, it may be that themore » levels of particle transport obtained in such cases [e.g. H-mode, ITB’s] are actually lower than is desirable for a practical fusion device. Ideally, one would be able to actively feedback control the turbulent transport, via manipulation of the flow profiles. The purpose of this research was to investigate the feasibility of using both advanced model-based control algorithms, as well as non-model-based algorithms, to control cross-field turbulence-driven particle transport through appropriate manipulation of radial plasma flow profiles. The University of New Mexico was responsible for the experimental portion of the project, while our collaborators at the University of Montana provided plasma transport modeling, and collaborators at Lehigh University developed and explored control methods.« less

Regulating Effect of Asymmetrical Impeller on the Flow Distributions of Double-sided Centrifugal Compressor

NASA Astrophysics Data System (ADS)

Yang, Ce; Liu, Yixiong; Yang, Dengfeng; Wang, Benjiang

2017-11-01

To achieve the rebalance of flow distributions of double-sided impellers, a method of improving the radius of rear impeller is presented in this paper. It is found that the flow distributions of front and rear impeller can be adjusted effectively by increasing the radius of rear impeller, thus improves the balance of flow distributions of front and rear impeller. Meanwhile, the working conversion mode process of double-sided centrifugal compressor is also changed. Further analysis shows that the flowrates of blade channels in front impeller are mainly influenced by the circumferential distributions of static pressure in the volute. But the flowrates of rear impeller blade channels are influenced by the outlet flow field of bent duct besides the effects of static pressure distributions in the volute. In the airflow interaction area downstream, the flowrate of blade channel is obviously smaller. By increasing the radius of rear impeller, the work capacity of rear impeller is enhanced, the working mode conversion process from parallel working mode of double-sided impeller to the single impeller working mode is delayed, and the stable working range of double-sided compressor is broadened.

Effect of flow rate and concentration difference on reverse electrodialysis system

NASA Astrophysics Data System (ADS)

Kwon, Kilsugn; Han, Jaesuk; Kim, Daejoong

2013-11-01

Various energy conversion technologies have been developed to reduce dependency on limited fossil fuels, including wind power, solar power, hydropower, ocean power, and geothermal power. Among them, reverse electrodialysis (RED), which is one type of salinity gradient power (SGP), has received much attention due to high reliability and simplicity without moving parts. Here, we experimentally evaluated the RED performance with several parameters like flow rate of concentrated and dilute solution, concentration difference, and temperature. RED was composed of endplates, electrodes, spacers, anion exchange membrane, and cation exchange membrane. Endplates are made by a polypropylene. It included the electrodes, flow field for the electrode rinse solution, and path to supply a concentrated and dilute solution. Titanium coated by iridium and ruthenium was used as the electrode. The electrode rinse solution based on hexacyanoferrate system is used to reduce the power loss generated by conversion process form ionic current to electric current. Maximum power monotonously increases as increasing flow rate and concentration difference. Net power has optimal point because pumping power consumption increases with flow rate. This work was supported by Basic Science Research Program (Grat No. NRF-2011-0009993) through the National Research Foundation of Korea.

Temperature and Atomic Oxygen Effects on Helium Leak Rates of a Candidate Main Interface Seal

NASA Technical Reports Server (NTRS)

Penney, Nicholas; Wasowski, Janice L.; Daniels, Christopher C.

2011-01-01

Helium leak tests were completed to characterize the leak rate of a 54 in. diameter composite space docking seal design in support of the National Aeronautics and Space Administration s (NASA's) Low Impact Docking System (LIDS). The evaluated seal design was a candidate for the main interface seal on the LIDS, which would be compressed between two vehicles, while docked, to prevent the escape of breathable air from the vehicles and into the vacuum of space. Leak tests completed at nominal temperatures of -30, 20, and 50 C on untreated and atomic oxygen (AO) exposed test samples were examined to determine the influence of both test temperature and AO exposure on the performance of the composite seal assembly. Results obtained for untreated seal samples showed leak rates which increased with increased test temperature. This general trend was not observed in tests of the AO exposed specimens. Initial examination of collected test data suggested that AO exposure resulted in higher helium leak rates, however, further analysis showed that the differences observed in the 20 and 50 C tests between the untreated and AO exposed samples were within the experimental error of the test method. Lack of discernable trends in the test data prevented concrete conclusions about the effects of test temperature and AO exposure on helium leak rates of the candidate seal design from being drawn. To facilitate a comparison of the current test data with results from previous leak tests using air as the test fluid, helium leak rates were converted to air leak rates using standard conversion factors for viscous and molecular flow. Flow rates calculated using the viscous flow conversion factor were significantly higher than the experimental air leakage values, whereas values calculated using the molecular flow conversion factor were significantly lower than the experimentally obtained air leak rates. The difference in these sets of converted flow rates and their deviation from the experimentally obtained air leak rate data suggest that neither conversion factor can be used alone to accurately convert helium leak rates to equivalent air leak rates for the test seals evaluated in this study; other leak phenomena, including permeation, must also be considered.

Novel Reactor Relevant RF Actuator Schemes for the Lower Hybrid and the Ion Cyclotron Range of Frequencies

NASA Astrophysics Data System (ADS)

Bonoli, Paul

2014-10-01

This paper presents a fresh physics perspective on the onerous problem of coupling and successfully utilizing ion cyclotron range of frequencies (ICRF) and lower hybrid range of frequencies (LHRF) actuators in the harsh environment of a nuclear fusion reactor. The ICRF and LH launchers are essentially first wall components in a fusion reactor and as such will be subjected to high heat fluxes. The high field side (HFS) of the plasma offers a region of reduced heat flux together with a quiescent scrape off layer (SOL). Placement of the ICRF and LHRF launchers on the tokamak HFS also offers distinct physics advantages: The higher toroidal magnetic field makes it possible to couple faster phase velocity LH waves that can penetrate farther into the plasma core and be absorbed by higher energy electrons, thereby increasing the current drive efficiency. In addition, re-location of the LH launcher off the mid-plane (i.e., poloidal ``steering'') allows further control of the deposition location. Also ICRF waves coupled from the HFS couple strongly to mode converted ion Bernstein waves and ion cyclotron waves waves as the minority density is increased, thus opening the possibility of using this scheme for flow drive and pressure control. Finally the quiescent nature of the HFS scrape off layer should minimize the effects of RF wave scattering from density fluctuations. Ray tracing / Fokker Planck simulations will be presented for LHRF applications in devices such as the proposed Advanced Divertor Experiment (ADX) and extending to ITER and beyond. Full-wave simulations will also be presented which demonstrate the possible combinations of electron and ion heating via ICRF mode conversion. Work supported by the US DoE under Contract Numbers DE-FC02-01ER54648 and DE-FC02-99ER54512.