Assessment of risks for high-speed rail grade crossings on the Empire Corridor : next generation high-speed rail program

DOT National Transportation Integrated Search

2000-08-01

The report describes a risk-based approach for assessing the implications of higher train speeds on highway-railroad grade crossing safety, and allocating limited resources to best reduce this risk. To predict accident frequency, an existing DOT mode...

Rotorcraft air transportation

NASA Technical Reports Server (NTRS)

Gilbert, G. A.

1983-01-01

Intermodal relationships and the particular ways in which they affect public transportation applications of rotorcraft are addressed. Some aspects of integrated services and general comparisons with other transportation modes are reviewed. Two potential application scenarios are discussed: down-to-downtown rotorcraft service and urban public transport rotorcraft service. It is concluded that to integrate well with ground access modes community rotorcraft service should be limited stop service with published schedules, and operate on a few specific routes between a few specific destinations. For downtown-to-downtown service, time savings favorable to rotorcraft are benefits that reflect its more direct access, relatively higher line-haul travel speeds, and less circuitous travel. For the scenario of public transport within urban areas, first, improving cruise speeds has a limited potential due to allowing for a ""station spacing'' effect. Secondly, public acceptance of higher acceleration/deceleration rates may be just as effective as a technological innovation as achieving higher cruise speeds.

Speed Profiles for Improvement of Maritime Emission Estimation.

PubMed

Yau, Pui Shan; Lee, Shun-Cheng; Ho, Kin Fai

2012-12-01

Maritime emissions play an important role in anthropogenic emissions, particularly for cities with busy ports such as Hong Kong. Ship emissions are strongly dependent on vessel speed, and thus accurate vessel speed is essential for maritime emission studies. In this study, we determined minute-by-minute high-resolution speed profiles of container ships on four major routes in Hong Kong waters using Automatic Identification System (AIS). The activity-based ship emissions of NO(x), CO, HC, CO(2), SO(2), and PM(10) were estimated using derived vessel speed profiles, and results were compared with those using the speed limits of control zones. Estimation using speed limits resulted in up to twofold overestimation of ship emissions. Compared with emissions estimated using the speed limits of control zones, emissions estimated using vessel speed profiles could provide results with up to 88% higher accuracy. Uncertainty analysis and sensitivity analysis of the model demonstrated the significance of improvement of vessel speed resolution. From spatial analysis, it is revealed that SO(2) and PM(10) emissions during maneuvering within 1 nautical mile from port were the highest. They contributed 7%-22% of SO(2) emissions and 8%-17% of PM(10) emissions of the entire voyage in Hong Kong.

Safety effects of reducing the speed limit from 90km/h to 70km/h.

PubMed

De Pauw, Ellen; Daniels, Stijn; Thierie, Melissa; Brijs, Tom

2014-01-01

Speed is one of the main risk factors in traffic safety, as it increases both the chances and the severity of a crash. In order to achieve improved traffic safety by influencing the speed of travel, road authorities may decide to lower the legally imposed speed limits. In 2001 the Flemish government decided to lower speed limits from 90km/h to 70km/h on a considerable number of highways. The present study examines the effectiveness of this measure using a comparison group before- and after study to account for general trend effects in road safety. Sixty-one road sections with a total length of 116km were included. The speed limits for those locations were restricted in 2001 and 2002. The comparison group consisted of 19 road sections with a total length of 53km and an unchanged speed limit of 90km/h throughout the research period. Taking trend into account, the analyses showed a 5% decrease [0.88; 1.03] in the crash rates after the speed limit restriction. A greater effect was identified in the case of crashes involving serious injuries and fatalities, which showed a decrease of 33% [0.57; 0.79]. Separate analyses between crashes at intersections and at road sections showed a higher effectiveness at road sections. It can be concluded from this study that speed limit restrictions do have a favorable effect on traffic safety, especially on severe crashes. Future research should examine the cause for the difference in the effect between road sections and intersections that was identified, taking vehicle speeds into account. Copyright © 2013 Elsevier Ltd. All rights reserved.

Frictional Torque on a Rotating Disc

ERIC Educational Resources Information Center

Mungan, Carl E.

2012-01-01

Resistance to motion often includes a dry frictional term independent of the speed of an object and a fluid drag term varying linearly with speed in the viscous limit. (At higher speeds, quadratic drag can also occur.) Here, measurements are performed for an aluminium disc mounted on bearings that is given an initial twist and allowed to spin…

[Attention to speed and guide traffic signs with eye movements].

PubMed

Conchillo Jiménez, Ángela; Pérez-Moreno, Elisa; Recarte Goldaracena, Miguel Ángel

2010-11-01

The goal of this research is to describe the visual search patterns for diverse traffic signs. Twelve drivers of both genders and different driving experience levels took part in real driving research with an instrumented car provided with an eye-tracking system. Looking at signs has a weak relation with speed reduction in cases where actual driving speed was higher. Nevertheless, among the people who looked at the sign, the percentage of those who reduce the speed below the limit is greater than of those who do not look at the sign. Guide traffic signs, particularly those mounted over the road, are more frequently glanced at than speed limit signs, with a glance duration of more than one second, in sequences of more than two consecutive fixations. Implications for driving and the possibilities and limitations of eye movement analysis for traffic sign research are discussed.

Peer influence predicts speeding prevalence among teenage drivers.

PubMed

Simons-Morton, Bruce G; Ouimet, Marie Claude; Chen, Rusan; Klauer, Sheila G; Lee, Suzanne E; Wang, Jing; Dingus, Thomas A

2012-12-01

Preventing speed-related crashes could reduce costs and improve efficiency in the transportation industry. This research examined the psychosocial and personality predictors of observed speeding among young drivers. Survey and driving data were collected from 42 newly-licensed teenage drivers during the first 18months of licensure. Speeding (i.e., driving 10mph over the speed limit; about 16km/h) was assessed by comparing speed data collected with recording systems installed in participants' vehicles with posted speed limits. Speeding was correlated with elevated g-force event rates (r=0.335, pb0.05), increased over time, and predicted by day vs. night trips, higher sensation seeking, substance use, tolerance of deviance, susceptibility to peer pressure, and number of risky friends. Perceived risk was a significant mediator of the association between speeding and risky friends. The findings support the contention that social norms may influence teenage speeding behavior and this relationship may operate through perceived risk. Copyright © 2012 National Safety Council and Elsevier Ltd. All rights reserved.

An investigation of the speeding-related crash designation through crash narrative reviews sampled via logistic regression.

PubMed

Fitzpatrick, Cole D; Rakasi, Saritha; Knodler, Michael A

2017-01-01

Speed is one of the most important factors in traffic safety as higher speeds are linked to increased crash risk and higher injury severities. Nearly a third of fatal crashes in the United States are designated as "speeding-related", which is defined as either "the driver behavior of exceeding the posted speed limit or driving too fast for conditions." While many studies have utilized the speeding-related designation in safety analyses, no studies have examined the underlying accuracy of this designation. Herein, we investigate the speeding-related crash designation through the development of a series of logistic regression models that were derived from the established speeding-related crash typologies and validated using a blind review, by multiple researchers, of 604 crash narratives. The developed logistic regression model accurately identified crashes which were not originally designated as speeding-related but had crash narratives that suggested speeding as a causative factor. Only 53.4% of crashes designated as speeding-related contained narratives which described speeding as a causative factor. Further investigation of these crashes revealed that the driver contributing code (DCC) of "driving too fast for conditions" was being used in three separate situations. Additionally, this DCC was also incorrectly used when "exceeding the posted speed limit" would likely have been a more appropriate designation. Finally, it was determined that the responding officer only utilized one DCC in 82% of crashes not designated as speeding-related but contained a narrative indicating speed as a contributing causal factor. The use of logistic regression models based upon speeding-related crash typologies offers a promising method by which all possible speeding-related crashes could be identified. Published by Elsevier Ltd.

Can anti-speeding messages based on protection motivation theory influence reported speeding intentions?

PubMed

Glendon, A Ian; Walker, Britta L

2013-08-01

The study investigated the effects of anti-speeding messages based on protection motivation theory (PMT) components: severity, vulnerability, rewards, self-efficacy, response efficacy, and response cost, on reported speeding intentions. Eighty-three participants aged 18-25 years holding a current Australian driver's license completed a questionnaire measuring their reported typical and recent speeding behaviors. Comparisons were made between 18 anti-speeding messages used on Australian roads and 18 new anti-speeding messages developed from the PMT model. Participants reported their reactions to the 36 messages on the perceived effectiveness of the message for themselves and for the general population of drivers, and also the likelihood of themselves and other drivers driving within the speed limit after viewing each message. Overall the PMT model-derived anti-speeding messages were better than jurisdiction-use anti-speeding messages in influencing participants' reported intention to drive within the speed limit. Severity and vulnerability were the most effective PMT components for developing anti-speeding messages. Male participants reported significantly lower intention to drive within the speed limit than did female participants. However, males reported significantly higher intention to drive within the speed limit for PMT-derived messages compared with jurisdiction-based messages. Third-person effects were that males reported anti-speeding messages to be more effective for the general driving population than for themselves. Females reported the opposite effect - that all messages would be more effective for themselves than for the general driving population. Findings provided support for using a sound conceptual basis as an effective foundation for anti-speeding message development as well as for evaluating proposed anti-speeding messages on the target driver population. Copyright © 2013 Elsevier Ltd. All rights reserved.

High Specific Stiffness Shafts and Advanced Bearing Coatings for Gas Turbine Engines Final Report CRADA No. TC-1089-95

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

Barbee, Troy; Chin, Herbert

At the time of the CRADA, the largest in-service gas-turbine aircraft engines strove for increased thrust and power density to meet the requirements for take-off thrust, given the increase in take-off gross weight (TOGW) associated with longer range transport requirements. The trend in modem turbo shaft engines was toward turbine shafts with higher and higher length-to-diameter ratios, which reduced the shaft critical speed. Using co nventional shaft materials, this lead to shafts that needed to operate near or above sensitive shaft bending critical speeds, therefore requiring multiple bearings and/ or multiple squeeze-film dampers to control the dynamic response. Using newmore » materials and d esign concepts this project demonstrated the use of new shaft materials which could provide increased shaft speed range above existing maximum engine speeds without encountering a critic al speed event and high vector deflections. This increased main shaft speed also resulted in decreased bearing life associated with lower heat dissipation and higher centrifugal forces. Thus, a limited effort was devoted to feasibility of higher performance bearing coatings to mitigate the speed effects.« less

Speed Profiles for Improvement of Maritime Emission Estimation

PubMed Central

Yau, Pui Shan; Lee, Shun-Cheng; Ho, Kin Fai

2012-01-01

Abstract Maritime emissions play an important role in anthropogenic emissions, particularly for cities with busy ports such as Hong Kong. Ship emissions are strongly dependent on vessel speed, and thus accurate vessel speed is essential for maritime emission studies. In this study, we determined minute-by-minute high-resolution speed profiles of container ships on four major routes in Hong Kong waters using Automatic Identification System (AIS). The activity-based ship emissions of NOx, CO, HC, CO2, SO2, and PM10 were estimated using derived vessel speed profiles, and results were compared with those using the speed limits of control zones. Estimation using speed limits resulted in up to twofold overestimation of ship emissions. Compared with emissions estimated using the speed limits of control zones, emissions estimated using vessel speed profiles could provide results with up to 88% higher accuracy. Uncertainty analysis and sensitivity analysis of the model demonstrated the significance of improvement of vessel speed resolution. From spatial analysis, it is revealed that SO2 and PM10 emissions during maneuvering within 1 nautical mile from port were the highest. They contributed 7%–22% of SO2 emissions and 8%–17% of PM10 emissions of the entire voyage in Hong Kong. PMID:23236250

Preliminary Results of the Determination of Inlet-Pressure Distortion Effects on Compressor Stall and Altitude Operating Limits of the J57-P-1 Turbojet Engine

NASA Technical Reports Server (NTRS)

Wallner, L. E.; Lubick, R. J.; Chelko, L. J.

1955-01-01

During an investigation of the J57-P-1 turbojet engine in the Lewis altitude wind tunnel, effects of inlet-flow distortion on engine stall characteristics and operating limits were determined. In addition to a uniform inlet-flow profile, the inlet-pressure distortions imposed included two radial, two circumferential, and one combined radial-circumferential profile. Data were obtained over a range of compressor speeds at an altitude of 50,000 and a flight Mach number of 0.8; in addition, the high- and low-speed engine operating limits were investigated up to the maximum operable altitude. The effect of changing the compressor bleed position on the stall and operating limits was determined for one of the inlet distortions. The circumferential distortions lowered the compressor stall pressure ratios; this resulted in less fuel-flow margin between steady-state operation and compressor stall. Consequently, the altitude operating Limits with circumferential distortions were reduced compared with the uniform inlet profile. Radial inlet-pressure distortions increased the pressure ratio required for compressor stall over that obtained with uniform inlet flow; this resulted in higher altitude operating limits. Likewise, the stall-limit fuel flows required with the radial inlet-pressure distortions were considerably higher than those obtained with the uniform inlet-pressure profile. A combined radial-circumferential inlet distortion had effects on the engine similar to the circumferential distortion. Bleeding air between the two compressors eliminated the low-speed stall limit and thus permitted higher altitude operation than was possible without compressor bleed.

Maximum walking speeds obtained using treadmill and overground robot system in persons with post-stroke hemiplegia

PubMed Central

2012-01-01

Background Previous studies demonstrated that stroke survivors have a limited capacity to increase their walking speeds beyond their self-selected maximum walking speed (SMWS). The purpose of this study was to determine the capacity of stroke survivors to reach faster speeds than their SMWS while walking on a treadmill belt or while being pushed by a robotic system (i.e. “push mode”). Methods Eighteen chronic stroke survivors with hemiplegia were involved in the study. We calculated their self-selected comfortable walking speed (SCWS) and SMWS overground using a 5-meter walk test (5-MWT). Then, they were exposed to walking at increased speeds, on a treadmill and while in “push mode” in an overground robotic device, the KineAssist, until they were tested at a speed that they could not sustain without losing balance. We recorded the time and number of steps during each trial and calculated gait speed, average cadence and average step length. Results Maximum walking speed in the “push mode” was 13% higher than the maximum walking speed on the treadmill and both were higher (“push mode”: 61%; treadmill: 40%) than the maximum walking speed overground. Subjects achieved these faster speeds by initially increasing both step length and cadence and, once individuals stopped increasing their step length, by only increasing cadence. Conclusions With post-stroke hemiplegia, individuals are able to walk at faster speeds than their SMWS overground, when provided with a safe environment that provides external forces that requires them to attempt dynamic stability maintenance at higher gait speeds. Therefore, this study suggests the possibility that, given the appropriate conditions, people post-stroke can be trained at higher speeds than previously attempted. PMID:23057500

Effects of vehicle power on passenger vehicle speeds.

PubMed

McCartt, Anne T; Hu, Wen

2017-07-04

During the past 2 decades, there have been large increases in mean horsepower and the mean horsepower-to-vehicle weight ratio for all types of new passenger vehicles in the United States. This study examined the relationship between travel speeds and vehicle power, defined as horsepower per 100 pounds of vehicle weight. Speed cameras measured travel speeds and photographed license plates and drivers of passenger vehicles traveling on roadways in Northern Virginia during daytime off-peak hours in spring 2013. The driver licensing agencies in the District of Columbia, Maryland, and Virginia provided vehicle information numbers (VINs) by matching license plate numbers with vehicle registration records and provided the age, gender, and ZIP code of the registered owner(s). VINs were decoded to obtain the curb weight and horsepower of vehicles. The study focused on 26,659 observed vehicles for which information on horsepower was available and the observed age and gender of drivers matched vehicle registration records. Log-linear regression estimated the effects of vehicle power on mean travel speeds, and logistic regression estimated the effects of vehicle power on the likelihood of a vehicle traveling over the speed limit and more than 10 mph over the limit. After controlling for driver characteristics, speed limit, vehicle type, and traffic volume, a 1-unit increase in vehicle power was associated with a 0.7% increase in mean speed, a 2.7% increase in the likelihood of a vehicle exceeding the speed limit by any amount, and an 11.6% increase in the likelihood of a vehicle exceeding the limit by 10 mph. All of these increases were highly significant. Speeding persists as a major factor in crashes in the United States. There are indications that travel speeds have increased in recent years. The current findings suggest the trend toward substantially more powerful vehicles may be contributing to higher speeds. Given the strong association between travel speed and crash risk and crash severity, this is cause for concern.

Digitally controlled analog proportional-integral-derivative (PID) controller for high-speed scanning probe microscopy

NASA Astrophysics Data System (ADS)

Dukic, Maja; Todorov, Vencislav; Andany, Santiago; Nievergelt, Adrian P.; Yang, Chen; Hosseini, Nahid; Fantner, Georg E.

2017-12-01

Nearly all scanning probe microscopes (SPMs) contain a feedback controller, which is used to move the scanner in the direction of the z-axis in order to maintain a constant setpoint based on the tip-sample interaction. The most frequently used feedback controller in SPMs is the proportional-integral (PI) controller. The bandwidth of the PI controller presents one of the speed limiting factors in high-speed SPMs, where higher bandwidths enable faster scanning speeds and higher imaging resolution. Most SPM systems use digital signal processor-based PI feedback controllers, which require analog-to-digital and digital-to-analog converters. These converters introduce additional feedback delays which limit the achievable imaging speed and resolution. In this paper, we present a digitally controlled analog proportional-integral-derivative (PID) controller. The controller implementation allows tunability of the PID gains over a large amplification and frequency range, while also providing precise control of the system and reproducibility of the gain parameters. By using the analog PID controller, we were able to perform successful atomic force microscopy imaging of a standard silicon calibration grating at line rates up to several kHz.

Digitally controlled analog proportional-integral-derivative (PID) controller for high-speed scanning probe microscopy.

PubMed

Dukic, Maja; Todorov, Vencislav; Andany, Santiago; Nievergelt, Adrian P; Yang, Chen; Hosseini, Nahid; Fantner, Georg E

2017-12-01

Nearly all scanning probe microscopes (SPMs) contain a feedback controller, which is used to move the scanner in the direction of the z-axis in order to maintain a constant setpoint based on the tip-sample interaction. The most frequently used feedback controller in SPMs is the proportional-integral (PI) controller. The bandwidth of the PI controller presents one of the speed limiting factors in high-speed SPMs, where higher bandwidths enable faster scanning speeds and higher imaging resolution. Most SPM systems use digital signal processor-based PI feedback controllers, which require analog-to-digital and digital-to-analog converters. These converters introduce additional feedback delays which limit the achievable imaging speed and resolution. In this paper, we present a digitally controlled analog proportional-integral-derivative (PID) controller. The controller implementation allows tunability of the PID gains over a large amplification and frequency range, while also providing precise control of the system and reproducibility of the gain parameters. By using the analog PID controller, we were able to perform successful atomic force microscopy imaging of a standard silicon calibration grating at line rates up to several kHz.

Demonstration, Testing and Qualification of a High Temperature, High Speed Magnetic Thrust Bearing

NASA Technical Reports Server (NTRS)

DeWitt, Kenneth

2005-01-01

The gas turbine industry has a continued interest in improving engine performance and reducing net operating and maintenance costs. These goals are being realized because of advancements in aeroelasticity, materials, and computational tools such as CFD and engine simulations. These advancements aid in increasing engine thrust-to-weight ratios, specific fuel consumption, pressure ratios, and overall reliability through higher speed, higher temperature, and more efficient engine operation. Currently, rolling element bearing and squeeze film dampers are used to support rotors in gas turbine engines. Present ball bearing configurations are limited in speed (<2 million DN) and temperature (<5OO F) and require both cooling air and an elaborate lubrication system. Also, ball bearings require extensive preventative maintenance in order to assure their safe operation. Since these bearings are at their operational limits, new technologies must be found in order to take advantage of other advances. Magnetic bearings are well suited to operate at extreme temperatures and higher rotational speeds and are a promising solution to the problems that conventional rolling element bearings present. Magnetic bearing technology is being developed worldwide and is considered an enabling technology for new engine designs. Using magnetic bearings, turbine and compressor spools can be radically redesigned to be significantly larger and stiffer with better damping and higher rotational speeds. These advances, a direct result of magnetic bearing technology, will allow significant increases in engine power and efficiency. Also, magnetic bearings allow for real-time, in-situ health monitoring of the system, lower maintenance costs and down time.

Impact of left ventricular assist device speed adjustment on exercise tolerance and markers of wall stress.

PubMed

Hayward, Christopher S; Salamonsen, Robert; Keogh, Anne M; Woodard, John; Ayre, Peter; Prichard, Roslyn; Kotlyar, Eugene; Macdonald, Peter S; Jansz, Paul; Spratt, Phillip

2015-09-01

Left ventricular assist devices are crucial in rehabilitation of patients with end-stage heart failure. Whether cardiopulmonary function is enhanced with higher pump output is unknown. 10 patients (aged 39±16 years, mean±SD) underwent monitored adjustment of pump speed to determine minimum safe low speed and maximum safe high speed at rest. Patients were then randomized to these speed settings and underwent three 6-minute walk tests (6MWT) and symptom-limited cardiopulmonary stress tests (CPX) on separate days. Pump speed settings (low, normal and high) resulted in significantly different resting pump flows of 4.43±0.6, 5.03±0.94, and 5.72±1.2 l/min (P<.001). There was a significant enhancement of pump flows (greater at higher speed settings) with exercise (P<0.05). Increased pump speed was associated with a trend to increased 6MWT distance (P=.10); and CPX exercise time (p=.27). Maximum workload achieved and peak oxygen consumption were significantly different comparing low to high pump speed settings only (P<.05). N-terminal-pro-B-type natriuretic peptide release was significantly reduced at higher pump speed with exercise (P<.01). We have found that alteration of pump speed setting resulted in significant variation in estimated pump flow. The high-speed setting was associated with lower natriuretic hormone release consistent with lower myocardial wall stress. This did not, however, improve exercise tolerance.

Peer Influence Predicts Speeding Prevalence Among Teenage Drivers

PubMed Central

Ouimet, Marie Claude; Chen, Rusan; Klauer, Sheila G.; Lee, Suzanne E.; Wang, Jing; Dingus, Thomas A.

2012-01-01

Objective This research examined the psychosocial and personality predictors of observed speeding among young drivers. Method. Survey and driving data were collected from 42 newly-licensed teenage drivers during the first 18 months of licensure. Speeding (i.e., driving 10 mph over the speed limit; about 16 km/h) was assessed by comparing speed data collected with recording systems installed in participants’ vehicles with posted speed limits. Questionnaire data collected at baseline were used to predict speeding rates using random effects regression analyses. For mediation analysis, data collected at baseline and at 6, 12, and 18 months after licensure were used. Results. Speeding was correlated with elevated g-force event rates, including hard braking and turning (r = 0.335, p < 0.05), but not with crashes and near crashes (r = 0.227; ns). Speeding prevalence increased over time. In univariate analyses speeding was predicted by day vs. night trips, higher sensation seeking, substance use, tolerance of deviance, susceptibility to peer pressure, and number of risky friends. In multivariate analyses the number of risky friends was the only significant predictor of speeding. Perceived risk was a significant mediator of the association between speeding and risky friends. Conclusion. The findings support the contention that social norms may influence teenage speeding behavior and this relationship may operate through perceived risk. PMID:23206513

Indicators of walking speed in rheumatoid arthritis: relative influence of articular, psychosocial, and body composition characteristics.

PubMed

Lusa, Amanda L; Amigues, Isabelle; Kramer, Henry R; Dam, Thuy-Tien; Giles, Jon T

2015-01-01

To explore the contributions from and interactions between articular swelling and damage, psychosocial factors, and body composition characteristics on walking speed in rheumatoid arthritis (RA). RA patients underwent the timed 400-meter long-corridor walk. Demographics, self-reported levels of depressive symptoms and fatigue, RA characteristics, and body composition (using whole-body dual X-ray absorptiometry, and abdominal and thigh computed tomography) were assessed and their associations with walking speed explored. A total of 132 RA patients had data for the 400-meter walk, among whom 107 (81%) completed the full 400 meters. Significant multivariable indicators of slower walking speed were older age, higher depression scores, higher reported pain and fatigue, higher swollen and replaced joint counts, higher cumulative prednisone exposure, nontreatment with disease-modifying antirheumatic drugs, and worse body composition. These features accounted for 60% of the modeled variability in walking speed. Among specific articular features, slower walking speed was primarily correlated with large/medium lower-extremity joint involvement. However, these articular features accounted for only 21% of the explainable variability in walking speed. Having any relevant articular characteristic was associated with a 20% lower walking speed among those with worse body composition (P < 0.001), compared with only a 6% lower speed among those with better body composition (P = 0.010 for interaction). Psychosocial factors and body composition are potentially reversible contributors to walking speed in RA. Relative to articular disease activity and damage, nonarticular indicators were collectively more potent indicators of an individual's mobility limitations. Copyright © 2015 by the American College of Rheumatology.

Prevalence, knowledge, attitude and practice of speeding in two districts in Kenya: Thika and Naivasha.

PubMed

Bachani, Abdulgafoor M; Hung, Yuen Wai; Mogere, Stephen; Akungah, Daniel; Nyamari, Jackim; Stevens, Kent A; Hyder, Adnan A

2013-12-01

In Kenya, RTIs had the second highest increase in disability-adjusted life years between 1990 and 2010, compared to other conditions. This study aims to determine the prevalence, knowledge, attitudes and practices for speeding in Thika and Naivasha districts in Kenya. Direct observations of vehicle speed were conducted at various times during the day and different days of the week on six roads selected based on a multi-stage sampling method in two districts to determine the prevalence of speeding. Roadside KAP interviews were administered to drivers, at motorcycle bays, petrol stations, and rest areas. Eight rounds of speed observations and four rounds of KAP interviews were conducted between July 2010 and November 2012. Results from the speeding observational studies show an overall high proportion of vehicles speeding above posted limits in both districts, with an average of 46.8% in Thika and 40.2% in Naivasha. Trend analysis revealed a greater decline in this prevalence in Thika (OR: 0.804, 95% CI: 0.793-0.814) than in Naivasha (OR: 0.932, 95% CI: 0.919-0.945) over the study period. On average, 58.8% of speeding vehicles in Thika and 57.2% of speeding vehicles in Naivasha travelled at 10 km/h or higher above speed limit. While the majority of respondents agreed that speeding is a cause of road traffic crashes in both Thika (70.3%) and Naivasha (68.7%), knowledge of speed limits at the location of the interview was limited. Enforcement levels also remained low, but subsequent rounds of data collection showed improvement, especially in Thika. This study demonstrates an improvement in the prevalence of speeding in two districts of Kenya over 2010-2012. It also highlights the need for further action to be taken to address the problem, and represents new data on speeding in Kenya and Africa. Copyright © 2013 Elsevier Ltd. All rights reserved.

Effectiveness and acceptance of the intelligent speeding prediction system (ISPS).

PubMed

Zhao, Guozhen; Wu, Changxu

2013-03-01

The intelligent speeding prediction system (ISPS) is an in-vehicle speed assistance system developed to provide quantitative predictions of speeding. Although the ISPS's prediction of speeding has been validated, whether the ISPS can regulate a driver's speed behavior or whether a driver accepts the ISPS needs further investigation. Additionally, compared to the existing intelligent speed adaptation (ISA) system, whether the ISPS performs better in terms of reducing excessive speeds and improving driving safety needs more direct evidence. An experiment was conducted to assess and compare the effectiveness and acceptance of the ISPS and the ISA. We conducted a driving simulator study with 40 participants. System type served as a between-subjects variable with four levels: no speed assistance system, pre-warning system developed based on the ISPS, post-warning system ISA, and combined pre-warning and ISA system. Speeding criterion served as a within-subjects variable with two levels: lower (posted speed limit plus 1 mph) and higher (posted speed limit plus 5 mph) speed threshold. Several aspects of the participants' driving speed, speeding measures, lead vehicle response, and subjective measures were collected. Both pre-warning and combined systems led to greater minimum time-to-collision. The combined system resulted in slower driving speed, fewer speeding exceedances, shorter speeding duration, and smaller speeding magnitude. The results indicate that both pre-warning and combined systems have the potential to improve driving safety and performance. Copyright © 2012 Elsevier Ltd. All rights reserved.

Cognitive function in the oldest old: women perform better than men.

PubMed

van Exel, E; Gussekloo, J; de Craen, A J; Bootsma-van der Wiel, A; Houx, P; Knook, D L; Westendorp, R G

2001-07-01

Limited formal education is associated with poor cognitive function. This could explain sex differences in cognitive function in the oldest old. Whether limited formal education explains differences in cognitive function between elderly women and men was explored. The Leiden 85-plus Study is a population based study investigating all 85 year old inhabitants of Leiden with an overall response rate of 87%. A sample of 599 participants were visited at their place of residence. The mini mental state examination was completed by all participants. Cognitive speed and memory were determined with four neuropsychological tests in participants with a mini mental state examination score higher than 18 points. The proportion of women with limited formal education was significantly higher than that of men (70% v 53%, p=0.001), but women had better scores for cognitive speed and memory than men (p<0.05). After adjustment for differences in limited formal education and the presence of depressive symptoms, the odds ratio for women to have a higher cognitive speed than men was 1.7 (95% CI; 1.0 to 2.6), and for them to have a better memory the odds ratio was 1.8 (95%CI; 1.2 to 2.7). Women have a better cognitive function than men, despite their lower level of formal education. Limited formal education alone, therefore, cannot explain the differences in cognitive function in women and men. These findings support the alternative hypothesis that biological differences, such as atherosclerosis, between women and men account for the sex differences in cognitive decline.

Measurement of whole-body vibration exposure from speed control humps

NASA Astrophysics Data System (ADS)

Khorshid, E.; Alkalby, F.; Kamal, H.

2007-07-01

The main objective of speed control humps is to introduce shocks and high vibration levels when a car passes over them if its speed is higher than the allowable limit. Hump geometry is a major factor in altering the level of these shocks and specifying the speed limit. However, there is no study of the relationship between whole body vibration due to passing over a speed control hump and lower back pain or occupational diseases. In this study, an experimental investigation is conducted to evaluate health risks associated with different geometry speed control humps. Vibration levels and shocks are measured by a seat pad accelerometer placed under the driver's seat to evaluate hazard risks on the human body's lower back. The assessment is based on two standard methods of measuring whole body vibration: the British standard BS 6841 and the new ISO/DIS standard 2631-5. These methods are used to assess the effects of vehicle type, passenger location in the vehicle, vehicle speed, and speed control hump geometry. It was found that circular speed control humps currently installed on many public roads should be modified in order to eliminate hazards. Two newly designed speed humps were proved to be less hazardous than circular speed control humps.

Air/sea DMS gas transfer in the North Atlantic: evidence for limited interfacial gas exchange at high wind speed

NASA Astrophysics Data System (ADS)

Bell, T. G.; De Bruyn, W.; Miller, S. D.; Ward, B.; Christensen, K.; Saltzman, E. S.

2013-05-01

Shipboard measurements of eddy covariance DMS air/sea fluxes and seawater concentration were carried out in the North Atlantic bloom region in June/July 2011. Gas transfer coefficients (k660) show a linear dependence on mean horizontal wind speed at wind speeds up to 11 m s-1. At higher wind speeds the relationship between k660 and wind speed weakens. At high winds, measured DMS fluxes were lower than predicted based on the linear relationship between wind speed and interfacial stress extrapolated from low to intermediate wind speeds. In contrast, the transfer coefficient for sensible heat did not exhibit this effect. The apparent suppression of air/sea gas flux at higher wind speeds appears to be related to sea state, as determined from shipboard wave measurements. These observations are consistent with the idea that long waves suppress near surface water side turbulence, and decrease interfacial gas transfer. This effect may be more easily observed for DMS than for less soluble gases, such as CO2, because the air/sea exchange of DMS is controlled by interfacial rather than bubble-mediated gas transfer under high wind speed conditions.

Air-sea dimethylsulfide (DMS) gas transfer in the North Atlantic: evidence for limited interfacial gas exchange at high wind speed

NASA Astrophysics Data System (ADS)

Bell, T. G.; De Bruyn, W.; Miller, S. D.; Ward, B.; Christensen, K.; Saltzman, E. S.

2013-11-01

Shipboard measurements of eddy covariance dimethylsulfide (DMS) air-sea fluxes and seawater concentration were carried out in the North Atlantic bloom region in June/July 2011. Gas transfer coefficients (k660) show a linear dependence on mean horizontal wind speed at wind speeds up to 11 m s-1. At higher wind speeds the relationship between k660 and wind speed weakens. At high winds, measured DMS fluxes were lower than predicted based on the linear relationship between wind speed and interfacial stress extrapolated from low to intermediate wind speeds. In contrast, the transfer coefficient for sensible heat did not exhibit this effect. The apparent suppression of air-sea gas flux at higher wind speeds appears to be related to sea state, as determined from shipboard wave measurements. These observations are consistent with the idea that long waves suppress near-surface water-side turbulence, and decrease interfacial gas transfer. This effect may be more easily observed for DMS than for less soluble gases, such as CO2, because the air-sea exchange of DMS is controlled by interfacial rather than bubble-mediated gas transfer under high wind speed conditions.

Flight Investigation of the Knock-Limited Performance of a Triptane Blend, a Toluene Blend, and 28-R Fuel in an R-1830-75 Engine

NASA Technical Reports Server (NTRS)

Blackman, Calvin C.

1946-01-01

Knock-limited performance data were obtained for three fuels on an R-1830-75 engine in a B-24D airplane at engine speeds of 1800, 2250, and 2600 rpm, a spark advance of 25 degrees B.T.C., and carburetor-air temperatures of 85 F for 1800 and 2250 rpm and 100 F for 2600 rpm. The test fuels were a blend of 80 percent 28-R plus 20 percent triptane (leaded to 4.5 ml TEL/gal), a blend of 80 percent 28-R plus 15 percent toluene (leaded to 4.5 ml TEL / gal), and 28-R fuel. The knock-limited manifold pressure of the toluene blend depreciated more in the lean region than the triptane blend or 28-R fuel. The knock-limited brake horsepower for the triptane blend varied from 16 to 25 percent higher than 28-R in the lean region and 18 to 30 percent higher in the rich region. The knock-limited brake horsepower of the toluene blend was approximately 15 percent higher than that of 28-R in the rich region and varied from 2 to 10 percent higher in the lean region. Knock limits of the triptane blend and 28-R fuel tested in the R-1830-75 engine agreed with limits for the same fuels determined with the R-1830-94 engine for engine speeds of 1800 and 2250 rpm.

Large motion high cycle high speed optical fibers for space based applications.

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

Stromberg, Peter G.; Tandon, Rajan; Gibson, Cory S.

2014-10-01

Future remote sensing applications will require higher resolution and therefore higher data rates (up to perhaps 100 gigabits per second) while achieving lower mass and cost. A current limitation to the design space is high speed high bandwidth data does not cross movable gimbals because of cabling issues. This requires the detectors to be off gimbal. The ability to get data across the gimbal would open up efficiencies in designs where the detectors and the electronics can be placed anywhere on the system. Fiber optic cables provide light weight high speed high bandwidth connections. Current options are limited to 20,000more » cycles as opposed to the 1,000,000 cycles needed for future space based applications. To extend this to the million+ regime, requires a thorough understanding of the failure mechanisms and the materials, proper selection of materials (e.g., glass and jacket material) allowable geometry changes to the cable, radiation hardness, etc.« less

Numerical modeling of probe velocity effects for electromagnetic NDE methods

NASA Astrophysics Data System (ADS)

Shin, Y. K.; Lord, W.

The present discussion of magnetic flux (MLF) leakage inspection introduces the behavior of motion-induced currents. The results obtained indicate that velocity effects exist at even low probe speeds for magnetic materials, compelling the inclusion of velocity effects in MLF testing of oil pipelines, where the excitation level and pig speed are much higher than those used in the present work. Probe velocity effect studies should influence probe design, defining suitable probe speed limits and establishing training guidelines for defect-characterization schemes.

Volterra equalization of complex modulation utilizing frequency chirp in directly modulated lasers

NASA Astrophysics Data System (ADS)

Hu, Shaohua; Yi, Xingwen; Zhang, Jing; Song, Yang; Zhu, Mingyue; Qiu, Kun

2018-02-01

We apply Volterra-based equalization for complex modulated optical signals utilizing the frequency chirp in DMLs. We experimentally demonstrate that the higher order Volterra filter is necessary in the higher speed transmissions. For further study, we isolate the adiabatic chirp by injection locking and realize the optical PM transmission. We make a comparison among IM, FM and PM with Volterra equalization, finding that PM and FM are more power insensitive and suitable for high speed, power limited fiber transmission. The performance can be further improved by exploiting the diversity gain.

Overt vs. covert speed cameras in combination with delayed vs. immediate feedback to the offender.

PubMed

Marciano, Hadas; Setter, Pe'erly; Norman, Joel

2015-06-01

Speeding is a major problem in road safety because it increases both the probability of accidents and the severity of injuries if an accident occurs. Speed cameras are one of the most common speed enforcement tools. Most of the speed cameras around the world are overt, but there is evidence that this can cause a "kangaroo effect" in driving patterns. One suggested alternative to prevent this kangaroo effect is the use of covert cameras. Another issue relevant to the effect of enforcement countermeasures on speeding is the timing of the fine. There is general agreement on the importance of the immediacy of the punishment, however, in the context of speed limit enforcement, implementing such immediate punishment is difficult. An immediate feedback that mediates the delay between the speed violation and getting a ticket is one possible solution. This study examines combinations of concealment and the timing of the fine in operating speed cameras in order to evaluate the most effective one in terms of enforcing speed limits. Using a driving simulator, the driving performance of the following four experimental groups was tested: (1) overt cameras with delayed feedback, (2) overt cameras with immediate feedback, (3) covert cameras with delayed feedback, and (4) covert cameras with immediate feedback. Each of the 58 participants drove in the same scenario on three different days. The results showed that both median speed and speed variance were higher with overt than with covert cameras. Moreover, implementing a covert camera system along with immediate feedback was more conducive to drivers maintaining steady speeds at the permitted levels from the very beginning. Finally, both 'overt cameras' groups exhibit a kangaroo effect throughout the entire experiment. It can be concluded that an implementation strategy consisting of covert speed cameras combined with immediate feedback to the offender is potentially an optimal way to motivate drivers to maintain speeds at the speed limit. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effect of mass and charge transport speed and direction in porous anodes on microbial electrolysis cell performance.

PubMed

Sleutels, Tom H J A; Hamelers, Hubertus V M; Buisman, Cees J N

2011-01-01

The use of porous electrodes like graphite felt as anode material has the potential of achieving high volumetric current densities. High volumetric current densities, however, may also lead to mass transport limitations within these porous materials. Therefore, in this study we investigated the mass and charge transport limitations by increasing the speed of the forced flow and changing the flow direction through the porous anode. Increase of the flow speed led to a decrease in current density when the flow was directed towards the membrane caused by an increase in anode resistance. Current density increased at higher flow speed when the flow was directed away from the membrane. This was caused by a decrease in transport resistance of ions through the membrane which increased the buffering effect of the system. Furthermore, the increase in flow speed led to an increase of the coulombic efficiency by 306%. Copyright © 2010 Elsevier Ltd. All rights reserved.

Spinal fusion limits upper body range of motion during gait without inducing compensatory mechanisms in adolescent idiopathic scoliosis patients.

PubMed

Holewijn, R M; Kingma, I; de Kleuver, M; Schimmel, J J P; Keijsers, N L W

2017-09-01

Previous studies show a limited alteration of gait at normal walking speed after spinal fusion surgery for adolescent idiopathic scoliosis (AIS), despite the presumed essential role of spinal mobility during gait. This study analyses how spinal fusion affects gait at more challenging walking speeds. More specifically, we investigated whether thoracic-pelvic rotations are reduced to a larger extent at higher gait speeds and whether compensatory mechanisms above and below the stiffened spine are present. 18 AIS patients underwent gait analysis at increasing walking speeds (0.45 to 2.22m/s) before and after spinal fusion. The range of motion (ROM) of the upper (thorax, thoracic-pelvic and pelvis) and lower body (hip, knee and ankle) was determined in all three planes. Spatiotemporal parameters of interest were stride length and cadence. Spinal fusion diminished transverse plane thoracic-pelvic ROM and this difference was more explicit at higher walking speeds. Transversal pelvis ROM was also decreased but this effect was not affected by speed. Lower body ROM, step length and cadence remained unaffected. Despite the reduction of upper body ROM after spine surgery during high speed gait, no altered spatiotemporal parameters or increased compensatory ROM above or below the fusion (i.e. in the shoulder girdle or lower extremities) was identified. Thus, it remains unclear how patients can cope so well with such major surgery. Future studies should focus on analyzing the kinematics of individual spinal levels above and below the fusion during gait to investigate possible compensatory mechanisms within the spine. Copyright © 2017 Elsevier B.V. All rights reserved.

Acceleration of small, light projectiles (including hydrogen isotopes) to high speeds using a two-stage light gas gun

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

Combs, S.K.; Foust, C.R.; Gouge, M.J.

1990-05-01

Small, light projectiles have been accelerated to high speeds using a two-stage light gas gun at Oak Ridge National Laboratory. With 35-mg plastic projectiles (4 mm in diameter), speeds of up to 4.5 km/s have been recorded. The pipe gun'' technique for freezing hydrogen isotopes {ital in} {ital situ} in the gun barrel has been used to accelerate deuterium pellets (nominal diameter of 4 mm) to velocities of up to 2.85 km/s. The primary application of this technology is for plasma fueling of fusion devices via pellet injection of hydrogen isotopes. Conventional pellet injectors are limited to pellet speeds inmore » the range 1--2 km/s. Higher velocities are desirable for plasma fueling applications, and the two-stage pneumatic technique offers performance in a higher velocity regime. However, experimental results indicate that the use of sabots to encase the cryogenic pellets and protect them from the high peak pressures will be required to reliably attain intact pellets at speeds of {approx}3 km/s or greater. In some limited tests, lithium hydride pellets were accelerated to speeds up to 4.2 km/s. Also, repetitive operation of the two-stage gun (four plastic pellets fired at {approx}0.5 Hz) was demonstrated for the first time in preliminary tests. The equipment and operation are described, and experimental results and some comparisons with a theoretical model are presented.« less

Acceleration of small, light projectiles (including hydrogen isotopes) to high speeds using a two-stage light gas gun

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

Combs, S.K.; Foust, C.R.; Gouge, M.J.

1989-01-01

Small, light projectiles have been accelerated to high speeds using a two-stage light gas gun at Oak Ridge National Laboratory. With 35-mg plastic projectiles (4 mm in diameter), speeds of up to 4.5 km/s have been recorded. The pipe gun'' technique for freezing hydrogen isotopes in situ in the gun barrel has been used to accelerate deuterium pellets (nominal diameter of 4 mm) to velocities of up to 2.85 km/s. The primary application of this technology is for plasma fueling of fusion devices via pellet injection of hydrogen isotopes. Conventional pellet injectors are limited to pellet speeds in the rangemore » 1-2 km/s. Higher velocities are desirable for plasma fueling applications, and the two-stage pneumatic technique offers performance in a higher velocity regime. However, experimental results indicate that the use of sabots to encase the cryogenic pellets and protect them for the high peak pressures will be required to reliably attain intact pellets at speeds of {approx}3 km/s or greater. In some limited tests, lithium hydride pellets were accelerated to speeds of up to 4.2 km/s. Also, repetitive operation of the two-stage gun (four plastic pellets fired at {approx}0.5 Hz) was demonstrated for the first time in preliminary tests. The equipment and operation are described, and experimental results and some comparisons with a theoretical model are presented. 17 refs., 6 figs., 2 tabs.« less

High speed galloping in the cheetah (Acinonyx jubatus) and the racing greyhound (Canis familiaris): spatio-temporal and kinetic characteristics.

PubMed

Hudson, Penny E; Corr, Sandra A; Wilson, Alan M

2012-07-15

The cheetah and racing greyhound are of a similar size and gross morphology and yet the cheetah is able to achieve a far higher top speed. We compared the kinematics and kinetics of galloping in the cheetah and greyhound to investigate how the cheetah can attain such remarkable maximum speeds. This also presented an opportunity to investigate some of the potential limits to maximum running speed in quadrupeds, which remain poorly understood. By combining force plate and high speed video data of galloping cheetahs and greyhounds, we show how the cheetah uses a lower stride frequency/longer stride length than the greyhound at any given speed. In some trials, the cheetahs used swing times as low as those of the greyhounds (0.2 s) so the cheetah has scope to use higher stride frequencies (up to 4.0 Hz), which may contribute to it having a higher top speed that the greyhound. Weight distribution between the animal's limbs varied with increasing speed. At high speed, the hindlimbs support the majority of the animal's body weight, with the cheetah supporting 70% of its body weight on its hindlimbs at 18 m s(-1); however, the greyhound hindlimbs support just 62% of its body weight. Supporting a greater proportion of body weight on a particular limb is likely to reduce the risk of slipping during propulsive efforts. Our results demonstrate several features of galloping and highlight differences between the cheetah and greyhound that may account for the cheetah's faster maximum speeds.

Running Speed Can Be Predicted from Foot Contact Time during Outdoor over Ground Running.

PubMed

de Ruiter, Cornelis J; van Oeveren, Ben; Francke, Agnieta; Zijlstra, Patrick; van Dieen, Jaap H

2016-01-01

The number of validation studies of commercially available foot pods that provide estimates of running speed is limited and these studies have been conducted under laboratory conditions. Moreover, internal data handling and algorithms used to derive speed from these pods are proprietary and thereby unclear. The present study investigates the use of foot contact time (CT) for running speed estimations, which potentially can be used in addition to the global positioning system (GPS) in situations where GPS performance is limited. CT was measured with tri axial inertial sensors attached to the feet of 14 runners, during natural over ground outdoor running, under optimized conditions for GPS. The individual relationships between running speed and CT were established during short runs at different speeds on two days. These relations were subsequently used to predict instantaneous speed during a straight line 4 km run with a single turning point halfway. Stopwatch derived speed, measured for each of 32 consecutive 125m intervals during the 4 km runs, was used as reference. Individual speed-CT relations were strong (r2 >0.96 for all trials) and consistent between days. During the 4km runs, median error (ranges) in predicted speed from CT 2.5% (5.2) was higher (P<0.05) than for GPS 1.6% (0.8). However, around the turning point and during the first and last 125m interval, error for GPS-speed increased to 5.0% (4.5) and became greater (P<0.05) than the error predicted from CT: 2.7% (4.4). Small speed fluctuations during 4km runs were adequately monitored with both methods: CT and GPS respectively explained 85% and 73% of the total speed variance during 4km runs. In conclusion, running speed estimates bases on speed-CT relations, have acceptable accuracy and could serve to backup or substitute for GPS during tarmac running on flat terrain whenever GPS performance is limited.

A Review of Vehicles Speed on School Safety Zone Areas in Pekanbaru City

NASA Astrophysics Data System (ADS)

Dwi Putri, Lusi; Soehardi, Fitridawati; Saleh, Alfian

2017-12-01

School Safety Zone is a location or region on particular roads that are time-based speed zone to set the speed of the vehicle in the school environment. The maximum speed limit permits entering a School Safety Zone, especially in Pekanbaru City is 25 km / h and an outline of the speed limit permit vehicles that pass through the School Safety Zone in Indonesia is generally 20-30 km / h. However, the vehicles speeds that pass School Safety Zone are higher than permit speeds.To ensure the level of vehicle offense across the territory of the School Safety Zone so it is necessary a primary data which is taken randomly based on field survey for 3 days at schools that has that facility ie SDN 3 Jalan Kesehatan Pekanbaru City, SDN 68 Jalan Balam Ujung Kota Pekanbaru and SDN 143 Jalan Taskurun Kota Pekanbaru. Furthermore, the data were taken in good condition that is at 6:30 to 7:30 am and at 12:00 to 13:00 pm. In addition, the data obtained is mileage and travel time of the vehicle. Both of these data can generate good speed value that passes through the area of School Safety Zone. Based on the research findings, the vehicle speed passing through the area of School Safety Zone is incompatible with speed permit at 35 km / h with a maximum average percentage of the rate of offense in the area of the school zone is 91.7%. This indicates that the vehicle passes School Safety Zone not following the rules of the maximum limit area and can be potentially harmful to elementary school students.

Overall Impact of Speed-Related Initiatives and Factors on Crash Outcomes

PubMed Central

D’Elia, A.; Newstead, S.; Cameron, M.

2007-01-01

From December 2000 until July 2002 a package of speed-related initiatives and factors took place in Victoria, Australia. The broad aim of this study was to evaluate the overall impact of the package on crash outcomes. Monthly crash counts and injury severity proportions were assessed using Poisson and logistic regression models respectively. The model measured the overall effect of the package after adjusting as far as possible for non-speed road safety initiatives and socio-economic factors. The speed-related package was associated with statistically significant estimated reductions in casualty crashes and suggested reductions in injury severity with trends towards increased reductions over time. From December 2000 until July 2002, three new speed enforcement initiatives were implemented in Victoria, Australia. These initiatives were introduced in stages and involved the following key components: More covert operations of mobile speed cameras, including flash-less operations; 50% increase in speed camera operating hours; and lowering of cameras’ speed detection threshold. In addition, during the period 2001 to 2002, the 50 km/h General Urban Speed Limit (GUSL) was introduced (January 2001), there was an increase in speed-related advertising including the “Wipe Off 5” campaign, media announcements were made related to the above enforcement initiatives and there was a speeding penalty restructure. The above elements combine to make up a package of speed-related initiatives and factors. The package represents a broad, long term program by Victorian government agencies to reduce speed based on three linked strategies: more intensive Police enforcement of speed limits to deter potential offenders, i.e. the three new speed enforcement initiatives just described - supported by higher penalties; a reduction in the speed limit on local streets throughout Victoria from 60 km/h to 50 km/h; and provision of information using the mass media (television, radio and billboard) to reinforce the benefits of reducing low level speeding - the central message of “Wipe Off 5”. These strategies were implemented across the entire state of Victoria with the intention of covering as many road users as possible. PMID:18184508

Driver speed selection on high-speed two-lane highways: Comparing speed profiles between uniform and differential speed limits.

PubMed

Russo, Brendan J; Savolainen, Peter T; Gates, Timothy J; Kay, Jonathan J; Frazier, Sterling

2017-07-04

Although a considerable amount of prior research has investigated the impacts of speed limits on traffic safety and operations, much of this research, and nearly all of the research related to differential speed limits, has been specific to limited access freeways. The unique safety and operational issues on highways without access control create difficulty relating the conclusions from prior freeway-related speed limit research to 2-lane highways, particularly research on differential limits due to passing limitations and subsequent queuing. Therefore, the objective of this study was to assess differences in driver speed selection with respect to the posted speed limit on rural 2-lane highways, with a particular emphasis on the differences between uniform and differential speed limits. Data were collected from nearly 59,000 vehicles across 320 sites in Montana and 4 neighboring states. Differences in mean speeds, 85th percentile speeds, and the standard deviation in speeds for free-flowing vehicles were examined across these sites using ordinary least squares regression models. Ultimately, the results of the analysis show that the mean speed, 85th percentile speed, and variability in travel speeds for free-flowing vehicles on 2-lane highways are generally lower at locations with uniform 65 mph speed limits, compared to locations with differential limits of 70 mph for cars and 60 mph for trucks. In addition to posted speed limits, several site characteristics were shown to influence speed selection including shoulder widths, frequency of horizontal curves, percentage of the segment that included no passing zones, and hourly volumes. Differences in vehicle speed characteristics were also observed between states, indicating that speed selection may also be influenced by local factors, such as driver population or enforcement.

High-Lift Systems on Commercial Subsonic Airliners

NASA Technical Reports Server (NTRS)

Rudolph, Peter K. C.

1996-01-01

The early breed of slow commercial airliners did not require high-lift systems because their wing loadings were low and their speed ratios between cruise and low speed (takeoff and landing) were about 2:1. However, even in those days the benefit of high-lift devices was recognized. Simple trailing-edge flaps were in use, not so much to reduce landing speeds, but to provide better glide-slope control without sideslipping the airplane and to improve pilot vision over the nose by reducing attitude during low-speed flight. As commercial-airplane cruise speeds increased with the development of more powerful engines, wing loadings increased and a real need for high-lift devices emerged to keep takeoff and landing speeds within reasonable limits. The high-lift devices of that era were generally trailing-edge flaps. When jet engines matured sufficiently in military service and were introduced commercially, airplane speed capability had to be increased to best take advantage of jet engine characteristics. This speed increase was accomplished by introducing the wing sweep and by further increasing wing loading. Whereas increased wing loading called for higher lift coefficients at low speeds, wing sweep actually decreased wing lift at low speeds. Takeoff and landing speeds increased on early jet airplanes, and, as a consequence, runways worldwide had to be lengthened. There are economical limits to the length of runways; there are safety limits to takeoff and landing speeds; and there are speed limits for tires. So, in order to hold takeoff and landing speeds within reasonable limits, more powerful high-lift devices were required. Wing trailing-edge devices evolved from plain flaps to Fowler flaps with single, double, and even triple slots. Wing leading edges evolved from fixed leading edges to a simple Krueger flap, and from fixed, slotted leading edges to two- and three-position slats and variable-camber (VC) Krueger flaps. The complexity of high-lift systems probably peaked on the Boeing 747, which has a VC Krueger flap and triple-slotted, inboard and outboard trailing-edge flaps. Since then, the tendency in high-lift system development has been to achieve high levels of lift with simpler devices in order to reduce fleet acquisition and maintenance costs. The intent of this paper is to: (1) review available high-lift devices, their functions, and design criteria; (2) appraise high-lift systems presently in service on commercial air liners; (3) present personal study results on high-lift systems; (4) develop a weight and cost model for high-lift systems; and (5) discuss the development tendencies of future high-lift systems.

Dynamic Speed Adaptation for Path Tracking Based on Curvature Information and Speed Limits.

PubMed

Gámez Serna, Citlalli; Ruichek, Yassine

2017-06-14

A critical concern of autonomous vehicles is safety. Different approaches have tried to enhance driving safety to reduce the number of fatal crashes and severe injuries. As an example, Intelligent Speed Adaptation (ISA) systems warn the driver when the vehicle exceeds the recommended speed limit. However, these systems only take into account fixed speed limits without considering factors like road geometry. In this paper, we consider road curvature with speed limits to automatically adjust vehicle's speed with the ideal one through our proposed Dynamic Speed Adaptation (DSA) method. Furthermore, 'curve analysis extraction' and 'speed limits database creation' are also part of our contribution. An algorithm that analyzes GPS information off-line identifies high curvature segments and estimates the speed for each curve. The speed limit database contains information about the different speed limit zones for each traveled path. Our DSA senses speed limits and curves of the road using GPS information and ensures smooth speed transitions between current and ideal speeds. Through experimental simulations with different control algorithms on real and simulated datasets, we prove that our method is able to significantly reduce lateral errors on sharp curves, to respect speed limits and consequently increase safety and comfort for the passenger.

Understanding the Benefits and Limitations of Increasing Maximum Rotor Tip Speed for Utility-Scale Wind Turbines

NASA Astrophysics Data System (ADS)

Ning, A.; Dykes, K.

2014-06-01

For utility-scale wind turbines, the maximum rotor rotation speed is generally constrained by noise considerations. Innovations in acoustics and/or siting in remote locations may enable future wind turbine designs to operate with higher tip speeds. Wind turbines designed to take advantage of higher tip speeds are expected to be able to capture more energy and utilize lighter drivetrains because of their decreased maximum torque loads. However, the magnitude of the potential cost savings is unclear, and the potential trade-offs with rotor and tower sizing are not well understood. A multidisciplinary, system-level framework was developed to facilitate wind turbine and wind plant analysis and optimization. The rotors, nacelles, and towers of wind turbines are optimized for minimum cost of energy subject to a large number of structural, manufacturing, and transportation constraints. These optimization studies suggest that allowing for higher maximum tip speeds could result in a decrease in the cost of energy of up to 5% for land-based sites and 2% for offshore sites when using current technology. Almost all of the cost savings are attributed to the decrease in gearbox mass as a consequence of the reduced maximum rotor torque. Although there is some increased energy capture, it is very minimal (less than 0.5%). Extreme increases in tip speed are unnecessary; benefits for maximum tip speeds greater than 100-110 m/s are small to nonexistent.

Design and performance of a punch mechanism based pellet injector for alternative injection in the large helical device

NASA Astrophysics Data System (ADS)

Mishra, J. S.; Sakamoto, R.; Motojima, G.; Matsuyama, A.; Yamada, H.

2011-02-01

A low speed single barrel pellet injector, using a mechanical punch device has been developed for alternative injection in the large helical device. A pellet is injected by the combined operation of a mechanical punch and a pneumatic propellant system. The pellet shape is cylindrical, 3 mm in diameter and 3 mm in length. Using this technique the speed of the pellet can be controlled flexibly in the range of 100-450 m/s, and a higher speed can be feasible for a higher gas pressure. The injector is equipped with a guide tube selector to direct the pellet to different injection locations. Pellets are exposed to several curved parts with the curvature radii Rc = 0.8 and 0.3 m when they are transferred in guided tubes to the respective injection locations. Pellet speed variation with pressure at different pellet formation temperatures has been observed. Pellet intactness tests through these guide tubes show a variation in the intact speed limit over a range of pellet formation temperatures from 6.5 to 9.8 K. Pellet speed reduction of less than 6% has been observed after the pellet moves through the curved guide tubes.

Dynamic Speed Adaptation for Path Tracking Based on Curvature Information and Speed Limits †

PubMed Central

Gámez Serna, Citlalli; Ruichek, Yassine

2017-01-01

A critical concern of autonomous vehicles is safety. Different approaches have tried to enhance driving safety to reduce the number of fatal crashes and severe injuries. As an example, Intelligent Speed Adaptation (ISA) systems warn the driver when the vehicle exceeds the recommended speed limit. However, these systems only take into account fixed speed limits without considering factors like road geometry. In this paper, we consider road curvature with speed limits to automatically adjust vehicle’s speed with the ideal one through our proposed Dynamic Speed Adaptation (DSA) method. Furthermore, ‘curve analysis extraction’ and ‘speed limits database creation’ are also part of our contribution. An algorithm that analyzes GPS information off-line identifies high curvature segments and estimates the speed for each curve. The speed limit database contains information about the different speed limit zones for each traveled path. Our DSA senses speed limits and curves of the road using GPS information and ensures smooth speed transitions between current and ideal speeds. Through experimental simulations with different control algorithms on real and simulated datasets, we prove that our method is able to significantly reduce lateral errors on sharp curves, to respect speed limits and consequently increase safety and comfort for the passenger. PMID:28613251

Criteria for setting speed limits in urban and suburban areas in Florida

DOT National Transportation Integrated Search

2003-03-01

Current methods of setting speed limits include maximum statutory limits by road class and geometric characteristics and speed zoning practice for the roads where the legislated limit does not reflect local differences. Speed limits in speed zones ar...

Simultaneous optical and meteor head echo measurements using the Middle Atmosphere Alomar Radar System (MAARSY): Data collection and preliminary analysis

NASA Astrophysics Data System (ADS)

Brown, P.; Stober, G.; Schult, C.; Krzeminski, Z.; Cooke, W.; Chau, J. L.

2017-07-01

The initial results of a two year simultaneous optical-radar meteor campaign are described. Analysis of 105 double-station optical meteors having plane of sky intersection angles greater than 5° and trail lengths in excess of 2 km also detected by the Middle Atmosphere Alomar Radar System (MAARSY) as head echoes was performed. These events show a median deviation in radiants between radar and optical determinations of 1.5°, with 1/3 of events having radiant agreement to less than one degree. MAARSY tends to record average speeds roughly 0.5 km/s and 1.3 km higher than optical records, in part due to the higher sensitivity of MAARSY as compared to the optical instruments. More than 98% of all head echoes are not detected with the optical system. Using this non-detection ratio and the known limiting sensitivity of the cameras, we estimate that the limiting meteoroid detection mass of MAARSY is in the 10-9-10-10 kg (astronomical limiting meteor magnitudes of +11 to +12) appropriate to speeds from 30 to 60 km/s. There is a clear trend of higher peak RCS for brighter meteors between 35 and -30 dBsm. For meteors with similar magnitudes, the MAARSY head echo radar cross-section is larger at higher speeds. Brighter meteors at fixed heights and similar speeds have consistently, on average, larger RCS values, in accordance with established scattering theory. However, our data show RCS ∝ v/2, much weaker than the normally assumed RCS ∝ v3, a consequence of our requiring head echoes to also be detectable optically. Most events show a smooth variation of RCS with height broadly following the light production behavior. A significant minority of meteors show large variations in RCS relative to the optical light curve over common height intervals, reflecting fragmentation or possibly differential ablation. No optically detected meteor occurring in the main radar beam and at times when the radar was collecting head echo data went unrecorded by MAARSY. Thus there does not appear to be any large scale bias in MAARSY head echo detections for the (comparatively) larger optical events in our dataset, even at very low speeds.

A speed limit compliance model for dynamic speed display sign.

PubMed

Ardeshiri, Anam; Jeihani, Mansoureh

2014-12-01

Violating speed limits is a major cause of motor vehicle crashes. Various techniques have been adopted to ensure that posted speed limits are obeyed by drivers. This study investigates the effect of dynamic speed display signs (DSDSs) on drivers' compliance with posted speed limit. An extensive speed data collection upstream of, adjacent to, and downstream of DSDS locations on multiple road classes with different speed limits (25, 35, and 45 mph) was performed short-term and long-term after DSDS installation. Conventional statistical analysis, regression models, and a Bayesian network were developed to assess the DSDS's effectiveness. General compliance with speed limit (upstream of the DSDS location), time of day, day of week, duration of DSDS operation, and distance from the DSDS location were significantly correlated with speed limit compliance adjacent to the DSDS. While compliance with the speed limit due to the DSDS increased by 5%, speed reduction occurred in 40% of the cases. Since drivers were likely to increase their speed after passing the DSDS, it should be installed on critical points supplemented with enforcement. Copyright © 2014 Elsevier Ltd. All rights reserved.

Overall impact of speed-related initiatives and factors on crash outcomes.

PubMed

D'Elia, A; Newstead, S; Cameron, M

2007-01-01

From December 2000 until July 2002 a package of speed-related initiatives and factors took place in Victoria, Australia. The broad aim of this study was to evaluate the overall impact of the package on crash outcomes. Monthly crash counts and injury severity proportions were assessed using Poisson and logistic regression models respectively. The model measured the overall effect of the package after adjusting as far as possible for non-speed road safety initiatives and socio-economic factors. The speed-related package was associated with statistically significant estimated reductions in casualty crashes and suggested reductions in injury severity with trends towards increased reductions over time. From December 2000 until July 2002, three new speed enforcement initiatives were implemented in Victoria, Australia. These initiatives were introduced in stages and involved the following key components: More covert operations of mobile speed cameras, including flash-less operations; 50% increase in speed camera operating hours; and lowering of cameras' speed detection threshold. In addition, during the period 2001 to 2002, the 50 km/h General Urban Speed Limit (GUSL) was introduced (January 2001), there was an increase in speed-related advertising including the "Wipe Off 5" campaign, media announcements were made related to the above enforcement initiatives and there was a speeding penalty restructure. The above elements combine to make up a package of speed-related initiatives and factors. The package represents a broad, long term program by Victorian government agencies to reduce speed based on three linked strategies: more intensive Police enforcement of speed limits to deter potential offenders, i.e. the three new speed enforcement initiatives just described - supported by higher penalties; a reduction in the speed limit on local streets throughout Victoria from 60 km/h to 50 km/h; and provision of information using the mass media (television, radio and billboard) to reinforce the benefits of reducing low level speeding - the central message of "Wipe Off 5". These strategies were implemented across the entire state of Victoria with the intention of covering as many road users as possible. This study aimed to evaluate the overall effectiveness of the speed-related package. The study objectives were: to document the increased speed camera activity in each speed limit zone and in Melbourne compared with the rest of Victoria; to evaluate the overall effect on crash outcomes of the package; to account as far as possible for the effect on crash outcomes of non-speed road safety initiatives and socio-economic factors, which would otherwise influence the speed-related package evaluation; and to examine speed trends in Melbourne and on Victorian rural highways, especially the proportions of vehicles travelling at excessive speeds. This paper presents the results of the evaluation of the overall impact on crash outcomes associated with the speed-related package, after adjusting as far as possible for the effect of non-speed road safety initiatives and socio-economic factors. D'Elia, Newstead and Cameron (2007) document the study results in full.

Maximum speed limits. Volume 2, The development of speed limits : a review of the literature

DOT National Transportation Integrated Search

1970-10-01

This report contains the literature review conducted as a part of the project "A Study for the Selection of Maximum Speed Limits." Five aspects of speed and speed control are discussed. These topics include: the history of speed limits; the relations...

Flight speed and performance of the wandering albatross with respect to wind.

PubMed

Richardson, Philip L; Wakefield, Ewan D; Phillips, Richard A

2018-01-01

Albatrosses and other large seabirds use dynamic soaring to gain sufficient energy from the wind to travel large distances rapidly and with little apparent effort. The recent development of miniature bird-borne tracking devices now makes it possible to explore the physical and biological implications of this means of locomotion in detail. Here we use GPS tracking and concurrent reanalyzed wind speed data to model the flight performance of wandering albatrosses Diomedea exulans soaring over the Southern Ocean. We investigate the extent to which flight speed and performance of albatrosses is facilitated or constrained by wind conditions encountered during foraging trips. We derived simple equations to model observed albatross ground speed as a function of wind speed and relative wind direction. Ground speeds of the tracked birds in the along-wind direction varied primarily by wind-induced leeway, which averaged 0.51 (± 0.02) times the wind speed at a reference height of 5 m. By subtracting leeway velocity from ground velocity, we were able to estimate airspeed (the magnitude of the bird's velocity through the air). As wind speeds increased from 3 to 18 m/s, the airspeed of wandering albatrosses flying in an across-wind direction increased by 0.42 (± 0.04) times the wind speed (i.e. ~ 6 m/s). At low wind speeds, tracked birds increased their airspeed in upwind flight relative to that in downwind flight. At higher wind speeds they apparently limited their airspeeds to a maximum of around 20 m/s, probably to keep the forces on their wings in dynamic soaring well within tolerable limits. Upwind airspeeds were nearly constant and downwind leeway increased with wind speed. Birds therefore achieved their fastest upwind ground speeds (~ 9 m/s) at low wind speeds (~ 3 m/s). This study provides insights into which flight strategies are optimal for dynamic soaring. Our results are consistent with the prediction that the optimal range speed of albatrosses is higher in headwind than tailwind flight but only in wind speeds of up to ~ 7 m/s. Our models predict that wandering albatrosses have oval-shaped airspeed polars, with the fastest airspeeds ~ 20 m/s centered in the across-wind direction. This suggests that in upwind flight in high winds, albatrosses can increase their ground speed by tacking like sailboats.

45 CFR 3.26 - Speed limit.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 45 Public Welfare 1 2011-10-01 2011-10-01 false Speed limit. 3.26 Section 3.26 Public Welfare... INSTITUTES OF HEALTH FEDERAL ENCLAVE Traffic Regulations § 3.26 Speed limit. The speed limit is 25 miles per hour, unless otherwise posted. A driver of a vehicle may not exceed the speed limit. ...

14 CFR 25.1505 - Maximum operating limit speed.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Maximum operating limit speed. 25.1505... Operating Limitations § 25.1505 Maximum operating limit speed. The maximum operating limit speed (V MO/M MO airspeed or Mach Number, whichever is critical at a particular altitude) is a speed that may not be...

14 CFR 25.1505 - Maximum operating limit speed.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Maximum operating limit speed. 25.1505... Operating Limitations § 25.1505 Maximum operating limit speed. The maximum operating limit speed (V MO/M MO airspeed or Mach Number, whichever is critical at a particular altitude) is a speed that may not be...

45 CFR 3.26 - Speed limit.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 45 Public Welfare 1 2010-10-01 2010-10-01 false Speed limit. 3.26 Section 3.26 Public Welfare... INSTITUTES OF HEALTH FEDERAL ENCLAVE Traffic Regulations § 3.26 Speed limit. The speed limit is 25 miles per hour, unless otherwise posted. A driver of a vehicle may not exceed the speed limit. ...

Adjusting for car occupant injury liability in relation to age, speed limit, and gender-specific driver crash involvement risk.

PubMed

Keall, Michael; Frith, William

2004-12-01

It is well established that older drivers' fragility is an important factor associated with higher levels of fatal crash involvement for older drivers. There has been less research on age-related fragility with respect to the sort of minor injuries that are more common in injury crashes. This study estimates a quantity that is related to injury fragility: the probability that a driver or a passenger of that driver will be injured in crashes involving two cars. The effects of other factors apart from drivers' fragility are included in this measure, including the fragility of the passengers, the crashworthiness of cars driven, seatbelt use by the occupants, and characteristics of crashes (including configuration and impact speed). The car occupant injury liability estimates appropriately includes these factors to adjust risk curves by age, gender, and speed limit accounting for overrepresentation in crashes associated with fragility and these other factors.

14 CFR 23.33 - Propeller speed and pitch limits.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Propeller speed and pitch limits. 23.33... Propeller speed and pitch limits. (a) General. The propeller speed and pitch must be limited to values that... the all engine(s) operating climb speed specified in § 23.65, the propeller must limit the engine r.p...

14 CFR 23.33 - Propeller speed and pitch limits.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Propeller speed and pitch limits. 23.33... Propeller speed and pitch limits. (a) General. The propeller speed and pitch must be limited to values that... the all engine(s) operating climb speed specified in § 23.65, the propeller must limit the engine r.p...

Safety and operational impacts of differential speed limits on two-lane rural highways in Montana.

DOT National Transportation Integrated Search

2016-07-01

Speed limit policies can be broadly classified into two categories. Uniform speed limit policies establish the same maximum limit for all vehicles, while differential speed limit policies set a lower limit for heavy trucks in comparison to cars and l...

Safety and operational impacts of differential speed limits on two-lane rural highways in Montana : project summary.

DOT National Transportation Integrated Search

2016-07-01

Speed limit policies can be broadly classified into two categories. Uniform speed limit policies establish the same maximum limit for all vehicles, while differential speed limit policies set a lower limit for heavy trucks in comparison to cars and l...

Traffic safety effects of new speed limits in Sweden.

PubMed

Vadeby, Anna; Forsman, Åsa

2018-05-01

The effects of speed, both positive and negative, make speed a primary target for policy action. Driving speeds affect the risk of being involved in a crash and the injury severity as well as the noise and exhaust emissions. Starting 2008, the Swedish Transport Administration performed a review of the speed limits on the national rural road network. This review resulted in major changes of the speed limits on the rural road network. It was predominantly roads with a low traffic safety standard and unsatisfactory road sides that were selected for reduced speed limits, as well as roads with a good traffic safety record being selected for an increase in speed limits. During 2008 and 2009, speed limit changed on approximately 20,500km of roads, out of which approximately 2700km were assigned an increase, and 17,800km were assigned a reduction in speed limits. The aim of this study is predominantly to describe and analyse the longterm traffic safety effect of increased, as well as, reduced speed limits, but also to analyse the changes in actual driving speeds due to the changed speed limits. Traffic safety effects are investigated by means of a before and after study with control group and the effects on actual mean speeds are measured by a sampling survey in which speed was measured at randomly selected sites before and after the speed limit changes. Results show a reduction in fatalities on rural roads with reduced speed limit from 90 to 80km/h where the number of fatalities decreased by 14 per year, while no significant changes were seen for the seriously injured. On motorways with an increased speed limit to 120km/h, the number of seriously injured increased by about 15 per year, but no significant changes were seen for the number of deaths. The number of seriously injured increased on all types of motorways, but the worst development was seen for narrow motorways (21.5m wide). For 2+1 roads (a continuous three-lane cross-section with alternating passing lanes and the two directions of travel separated by a median barrier) with decreased speed limit from 110 to 100km/h, the seriously injured decreased by about 16 per year. As regards the change of mean speeds, a decrease in speed limit with 10km/h led to a decrease of mean speeds of around 2-3km/h and an increase of the speed limit with 10km/h resulted in an increase of mean speed by 3km/h. In conclusion, the results show that in total about 17 lives per year have been saved on the road network with changed speed limits. For comparison, 397 road users were killed in total during 2008. The number of seriously injured remain in principle unchanged. It should also be noted that the results are obtained for the road network which changed the speed limits during 2008 and 2009, and it is not certain that the results can be generalised to another road network. Copyright © 2017 Elsevier Ltd. All rights reserved.

High-Speed Videography Overview

NASA Astrophysics Data System (ADS)

Miller, C. E.

1989-02-01

The field of high-speed videography (HSV) has continued to mature in recent years, due to the introduction of a mixture of new technology and extensions of existing technology. Recent low frame-rate innovations have the potential to dramatically expand the areas of information gathering and motion analysis at all frame-rates. Progress at the 0 - rate is bringing the battle of film versus video to the field of still photography. The pressure to push intermediate frame rates higher continues, although the maximum achievable frame rate has remained stable for several years. Higher maximum recording rates appear technologically practical, but economic factors impose severe limitations to development. The application of diverse photographic techniques to video-based systems is under-exploited. The basics of HSV apply to other fields, such as machine vision and robotics. Present motion analysis systems continue to function mainly as an instant replay replacement for high-speed movie film cameras. The interrelationship among lighting, shuttering and spatial resolution is examined.

14 CFR 25.1516 - Other speed limitations.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Other speed limitations. 25.1516 Section 25.1516 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... Limitations § 25.1516 Other speed limitations. Any other limitation associated with speed must be established...

14 CFR 25.1516 - Other speed limitations.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Other speed limitations. 25.1516 Section 25.1516 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... Limitations § 25.1516 Other speed limitations. Any other limitation associated with speed must be established...

A simple way to higher speed atomic force microscopy by retrofitting with a novel high-speed flexure-guided scanner

NASA Astrophysics Data System (ADS)

Ouma Alunda, Bernard; Lee, Yong Joong; Park, Soyeun

2018-06-01

A typical line-scan rate for a commercial atomic force microscope (AFM) is about 1 Hz. At such a rate, more than four minutes of scanning time is required to obtain an image of 256 × 256 pixels. Despite control electronics of most commercial AFMs permit faster scan rates, default piezoelectric X–Y scanners limit the overall speed of the system. This is a direct consequence of manufacturers choosing a large scan range over the maximum operating speed for a X–Y scanner. Although some AFM manufacturers offer reduced-scan area scanners as an option, the speed improvement is not significant because such scanners do not have large enough reduction in the scan range and are mainly targeted to reducing the overall cost of the AFM systems. In this article, we present a simple parallel-kinematic substitute scanner for a commercial atomic force microscope to afford a higher scanning speed with no other hardware or software upgrade to the original system. Although the scan area reduction is unavoidable, our modified commercial XE-70 AFM from Park Systems has achieved a line scan rate of over 50 Hz, more than 10 times faster than the original, unmodified system. Our flexure-guided X–Y scanner can be a simple drop-in replacement option for enhancing the speed of various aging atomic force microscopes.

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

Herfst, Rodolf; Dekker, Bert; Witvoet, Gert

One of the major limitations in the speed of the atomic force microscope (AFM) is the bandwidth of the mechanical scanning stage, especially in the vertical (z) direction. According to the design principles of “light and stiff” and “static determinacy,” the bandwidth of the mechanical scanner is limited by the first eigenfrequency of the AFM head in case of tip scanning and by the sample stage in terms of sample scanning. Due to stringent requirements of the system, simply pushing the first eigenfrequency to an ever higher value has reached its limitation. We have developed a miniaturized, high speed AFMmore » scanner in which the dynamics of the z-scanning stage are made insensitive to its surrounding dynamics via suspension of it on specific dynamically determined points. This resulted in a mechanical bandwidth as high as that of the z-actuator (50 kHz) while remaining insensitive to the dynamics of its base and surroundings. The scanner allows a practical z scan range of 2.1 μm. We have demonstrated the applicability of the scanner to the high speed scanning of nanostructures.« less

Demonstration of variable speed permanent magnet generator at small, low-head hydro site

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

Brown Kinloch, David

Small hydro developers face a limited set of bad choices when choosing a generator for a small low-head hydro site. Direct drive synchronous generators are expensive and technically complex to install. Simpler induction generators are higher speed, requiring a speed increaser, which results in inefficiencies and maintenance problems. In addition, both induction and synchronous generators turn at a fixed speed, causing the turbine to run off its peak efficiency curve whenever the available head is different than the designed optimum head.The solution to these problems is the variable speed Permanent Magnet Generators (PMG). At the Weisenberger Mill in Midway, KY,more » a variable speed Permanent Magnet Generator has been installed and demonstrated. This new PMG system replaced an existing induction generator that had a HTD belt drive speed increaser system. Data was taken from the old generator before it was removed and compared to data collected after the PMG system was installed. The new variable speed PMG system is calculated to produce over 96% more energy than the old induction generator system during an average year. This significant increase was primarily due to the PMG generator operating at the correct speed at the maximum head, and the ability for the PMG generator to reduce its speed to lower optimum speeds as the stream flow increased and the net head decreased.This demonstration showed the importance of being able to adjust the speed of fixed blade turbines. All fixed blade turbines with varying net heads could achieve higher efficiencies if the speed can be matched to the optimum speed as the head changes. In addition, this demonstration showed that there are many potential efficiencies that could be realized with variable speed technology at hydro sites where mismatched turbine and generator speeds result in lower power output, even at maximum head. Funding for this project came from the US Dept. of Energy, through Award Number DE-EE0005429.« less

Spatial regression analysis of traffic crashes in Seoul.

PubMed

Rhee, Kyoung-Ah; Kim, Joon-Ki; Lee, Young-ihn; Ulfarsson, Gudmundur F

2016-06-01

Traffic crashes can be spatially correlated events and the analysis of the distribution of traffic crash frequency requires evaluation of parameters that reflect spatial properties and correlation. Typically this spatial aspect of crash data is not used in everyday practice by planning agencies and this contributes to a gap between research and practice. A database of traffic crashes in Seoul, Korea, in 2010 was developed at the traffic analysis zone (TAZ) level with a number of GIS developed spatial variables. Practical spatial models using available software were estimated. The spatial error model was determined to be better than the spatial lag model and an ordinary least squares baseline regression. A geographically weighted regression model provided useful insights about localization of effects. The results found that an increased length of roads with speed limit below 30 km/h and a higher ratio of residents below age of 15 were correlated with lower traffic crash frequency, while a higher ratio of residents who moved to the TAZ, more vehicle-kilometers traveled, and a greater number of access points with speed limit difference between side roads and mainline above 30 km/h all increased the number of traffic crashes. This suggests, for example, that better control or design for merging lower speed roads with higher speed roads is important. A key result is that the length of bus-only center lanes had the largest effect on increasing traffic crashes. This is important as bus-only center lanes with bus stop islands have been increasingly used to improve transit times. Hence the potential negative safety impacts of such systems need to be studied further and mitigated through improved design of pedestrian access to center bus stop islands. Copyright © 2016 Elsevier Ltd. All rights reserved.

14 CFR 27.33 - Main rotor speed and pitch limits.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Main rotor speed and pitch limits. 27.33... AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Flight General § 27.33 Main rotor speed and pitch limits. (a) Main rotor speed limits. A range of main rotor speeds must be established that— (1) With power on...

14 CFR 29.33 - Main rotor speed and pitch limits.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Main rotor speed and pitch limits. 29.33... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Flight General § 29.33 Main rotor speed and pitch limits. (a) Main rotor speed limits. A range of main rotor speeds must be established that— (1) With power on...

14 CFR 29.33 - Main rotor speed and pitch limits.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Main rotor speed and pitch limits. 29.33... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Flight General § 29.33 Main rotor speed and pitch limits. (a) Main rotor speed limits. A range of main rotor speeds must be established that— (1) With power on...

14 CFR 27.33 - Main rotor speed and pitch limits.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Main rotor speed and pitch limits. 27.33... AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Flight General § 27.33 Main rotor speed and pitch limits. (a) Main rotor speed limits. A range of main rotor speeds must be established that— (1) With power on...

Evaluating the impacts of proposed speed limit increases in Michigan : research spotlight.

DOT National Transportation Integrated Search

2014-07-01

Recent proposed speed limit legislation led MDOT to evaluate the : states current speed limit policies and potential alternatives. Currently, : Michigan freeways have a maximum speed limit of 70 mph for passenger : vehicles and 60 mph for trucks a...

Are Students Aware of the Speed Limits on a University Campus?

ERIC Educational Resources Information Center

Brooks, Johnell; Raines, Stephanie; Klein, Nathan; Crisler, Matt; Wills, Rebekkah; Mossey, Mary; Koon, Beatrice; McKibben, Eric; Ogle, Jennifer; Robinson, Geary

2010-01-01

Driving speed is an important traffic safety issue. The lack of adherence to posted speed limits is a safety concern, especially on university campuses where the populations of drivers are at increased risk for crashes involving speeding due to their young age. Thus, driver speed and knowledge of speed limits on university campuses is an important…

Safe speed limits for a safe system: The relationship between speed limit and fatal crash rate for different crash types.

PubMed

Doecke, Sam D; Kloeden, Craig N; Dutschke, Jeffrey K; Baldock, Matthew R J

2018-05-19

The objective of this article is to provide empirical evidence for safe speed limits that will meet the objectives of the Safe System by examining the relationship between speed limit and injury severity for different crash types, using police-reported crash data. Police-reported crashes from 2 Australian jurisdictions were used to calculate a fatal crash rate by speed limit and crash type. Example safe speed limits were defined using threshold risk levels. A positive exponential relationship between speed limit and fatality rate was found. For an example fatality rate threshold of 1 in 100 crashes it was found that safe speed limits are 40 km/h for pedestrian crashes; 50 km/h for head-on crashes; 60 km/h for hit fixed object crashes; 80 km/h for right angle, right turn, and left road/rollover crashes; and 110 km/h or more for rear-end crashes. The positive exponential relationship between speed limit and fatal crash rate is consistent with prior research into speed and crash risk. The results indicate that speed zones of 100 km/h or more only meet the objectives of the Safe System, with regard to fatal crashes, where all crash types except rear-end crashes are exceedingly rare, such as on a high standard restricted access highway with a safe roadside design.

Modified Redundancy based Technique—a New Approach to Combat Error Propagation Effect of AES

NASA Astrophysics Data System (ADS)

Sarkar, B.; Bhunia, C. T.; Maulik, U.

2012-06-01

Advanced encryption standard (AES) is a great research challenge. It has been developed to replace the data encryption standard (DES). AES suffers from a major limitation of error propagation effect. To tackle this limitation, two methods are available. One is redundancy based technique and the other one is bite based parity technique. The first one has a significant advantage of correcting any error on definite term over the second one but at the cost of higher level of overhead and hence lowering the processing speed. In this paper, a new approach based on the redundancy based technique is proposed that would certainly speed up the process of reliable encryption and hence the secured communication.

The status of analytical preparation for 2-dimensional testing at high transonic speeds in the University of Southampton transonic self-streamlining wind tunnel

NASA Technical Reports Server (NTRS)

Lewis, M. C.

1984-01-01

Validation data from the Transonic Self-Streamlining Wind Tunnel has proved the feasibility of streamlining two dimensional flexible walls at low speeds and up to transonic speeds, the upper limit being the speed where the flexible walls are just supercritical. At this condition, breakdown of the wall setting strategy is evident in that convergence is neither as rapid nor as stable as for lower speeds, and wall streamlining criteria are not always completely satisfied. The only major step necessary to permit the extension of two dimensional testing into higher transonic speeds is the provision of a rapid algorithm to solve for mixed flow in the imagery flow fields. The status of two dimensional high transonic testing in the Transonic Self-Streamlining Wind Tunnel is outlined and, in particular, the progress of adapting an algorithm, which solves the Transonic Small Perturbation Equation, for predicting the imagery flow fields is detailed.

Relativistic Spacecraft Propelled by Directed Energy

NASA Astrophysics Data System (ADS)

Kulkarni, Neeraj; Lubin, Philip; Zhang, Qicheng

2018-04-01

Achieving relativistic flight to enable extrasolar exploration is one of the dreams of humanity and the long-term goal of our NASA Starlight program. We derive a relativistic solution for the motion of a spacecraft propelled by radiation pressure from a directed energy (DE) system. Depending on the system parameters, low-mass spacecraft can achieve relativistic speeds, thus enabling interstellar exploration. The diffraction of the DE system plays an important role and limits the maximum speed of the spacecraft. We consider “photon recycling” as a possible method to achieving higher speeds. We also discuss recent claims that our previous work on this topic is incorrect and show that these claims arise from an improper treatment of causality.

High performance cryogenic turboexpanders

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

Agahi, R.R.; Ershaghi, B.; Lin, M.C.

1996-12-31

The use of turboexpanders for deep cryogenic temperatures has been constrained because of thermal efficiency limitations. This limited thermal efficiency was mostly due to mechanical constraints. Recent improvements in analytical techniques, bearing technology, and design features have made it possible to design and operate turboexpanders at more favorable conditions, such as of higher rotational speeds. Several turboexpander installations in helium and hydrogen processes have shown a significant improvement in plant performance over non-turboexpander options.

Analysis of inconsistencies related to design speed, operating speed, and speed limits.

DOT National Transportation Integrated Search

2004-02-01

The objective of this research was to examine the relationship among design speeds, operating speeds and speed limits and address safety and operational concerns regarding the presence of disparities among these speed metrics. Roadway sections were s...

50 CFR 38.13 - Speed limits.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 50 Wildlife and Fisheries 6 2010-10-01 2010-10-01 false Speed limits. 38.13 Section 38.13 Wildlife... NATIONAL WILDLIFE REFUGE SYSTEM MIDWAY ATOLL NATIONAL WILDLIFE REFUGE Prohibitions § 38.13 Speed limits. No person on Midway Atoll National Wildlife Refuge will exceed the speed limit for automobiles, trucks...

Automated section speed control on motorways: an evaluation of the effect on driving speed.

PubMed

De Pauw, Ellen; Daniels, Stijn; Brijs, Tom; Hermans, Elke; Wets, Geert

2014-12-01

Automated section speed control is a fairly new traffic safety measure that is increasingly applied to enforce speed limits. The advantage of this enforcement system is the registration of the average speed at an entire section, which would lead to high speed limit compliances and subsequently to a reduction in the vehicle speed variability, increased headway, more homogenised traffic flow and increased traffic capacity. However, the number of studies that analysed these effects are limited. The present study evaluates the speed effect of two section speed control systems in Flanders, Belgium. Both sections are located in the opposite direction of a three-lane motorway with a posted speed limit of 120 km/h. Speed data were collected at different points: from 6 km before the entrance of the section to 6 km downstream from the section. The effect was analysed through a before- and after comparison of travel speeds. General time trends and fluctuations were controlled through the analysis of speeds at comparison locations. On the enforced sections considerable decreases were found of about 5.84 km/h in the average speed, 74% in the odds of drivers exceeding the speed limit and 86% in the odds of drivers exceeding the speed limit by more than 10%. At the locations up- and downstream from the section also favourable effects were found for the three outcomes. Furthermore a decrease in the speed variability could be observed at all these data points. Copyright © 2014 Elsevier Ltd. All rights reserved.

14 CFR 25.1583 - Operating limitations.

Code of Federal Regulations, 2010 CFR

2010-01-01

... any regime of flight (climb, cruise, or descent) unless a higher speed is authorized for flight test... and aileron controls, as well as maneuvers that involve angles of attack near the stall, should be... and balance control and loading document that is incorporated by reference in the Airplane Flight...

Quantum Speed Limits across the Quantum-to-Classical Transition

NASA Astrophysics Data System (ADS)

Shanahan, B.; Chenu, A.; Margolus, N.; del Campo, A.

2018-02-01

Quantum speed limits set an upper bound to the rate at which a quantum system can evolve. Adopting a phase-space approach, we explore quantum speed limits across the quantum-to-classical transition and identify equivalent bounds in the classical world. As a result, and contrary to common belief, we show that speed limits exist for both quantum and classical systems. As in the quantum domain, classical speed limits are set by a given norm of the generator of time evolution.

Sprinting performance of two Iberian fish: Luciobarbus bocagei and Pseudochondrostoma duriense in an open channel flume

USGS Publications Warehouse

Sanz-Ronda, Francisco Javier; Ruiz-Legazpi, Jorge; Bravo-Cordoba, Francisco Javier; Makrakis, Sergio; Castro-Santos, Theodore R.

2015-01-01

This paper presents sprinting data from Iberian barbel (Luciobarbus bocagei) and northern straight-mouth nase (Pseudochondrostoma duriense), volitionally swimming against high velocity flows (1.5, 2.5 and 3 m s−1) in an open channel flume. Swimming endurance and speed greatly exceeded previously published observations with both species attaining swim speeds >20 body lengths s−1. Flow velocity was the primary variable limiting the distance both species were able to traverse. Barbel swam greater distances than nase at higher flow velocities, with longer individuals attaining greater distances than smaller ones. The results challenge established fish passage guidelines, suggesting that in some cases these species are capable of passing much higher velocities than was previously believed.

Effects of weather conditions, light conditions, and road lighting on vehicle speed.

PubMed

Jägerbrand, Annika K; Sjöbergh, Jonas

2016-01-01

Light conditions are known to affect the number of vehicle accidents and fatalities but the relationship between light conditions and vehicle speed is not fully understood. This study examined whether vehicle speed on roads is higher in daylight and under road lighting than in darkness, and determined the combined effects of light conditions, posted speed limit and weather conditions on driving speed. The vehicle speed of passenger cars in different light conditions (daylight, twilight, darkness, artificial light) and different weather conditions (clear weather, rain, snow) was determined using traffic and weather data collected on an hourly basis for approximately 2 years (1 September 2012-31 May 2014) at 25 locations in Sweden (17 with road lighting and eight without). In total, the data included almost 60 million vehicle passes. The data were cleaned by removing June, July, and August, which have different traffic patterns than the rest of the year. Only data from the periods 10:00 A.M.-04:00 P.M. and 06:00 P.M.-10:00 P.M. were used, to remove traffic during rush hour and at night. Multivariate adaptive regression splines was used to evaluate the overall influence of independent variables on vehicle speed and nonparametric statistical testing was applied to test for speed differences between dark-daylight, dark-twilight, and twilight-daylight, on roads with and without road lighting. The results show that vehicle speed in general depends on several independent variables. Analyses of vehicle speed and speed differences between daylight, twilight and darkness, with and without road lighting, did not reveal any differences attributable to light conditions. However, vehicle speed decreased due to rain or snow and the decrease was higher on roads without road lighting than on roads with lighting. These results suggest that the strong association between traffic accidents and darkness or low light conditions could be explained by drivers failing to adjust their speed to the reduced visibility in dark conditions.

Speed limit recommendation in vicinity of signalized, high-speed intersection.

DOT National Transportation Integrated Search

2012-04-01

We evaluated the traffic operations and safety effects of 5 mph and 10 mph speed limit reductions in the vicinity of highspeed, : signalized intersections with advance warning flashers (AWF). Traffic operational effects of the reduced speed : limits ...

Stopbands in the existence domains of acoustic solitons

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

Nsengiyumva, F., E-mail: franco.nseng@gmail.com; Hellberg, M. A., E-mail: hellberg@ukzn.ac.za; Mace, R. L., E-mail: macer@ukzn.ac.za

2014-10-15

A fully nonlinear Sagdeev pseudopotential approach is used to study the existence domain of fast mode ion-acoustic solitons in a three-species plasma composed of cold and warm adiabatic positive ion species and Boltzmann electrons. It is shown that for appropriate values of the cold-to-warm ion charge-to-mass ratio, μ, and the effective warm ion-to-electron temperature ratio, τ, there is a range in cold to warm ion charge density ratio, f, over which a stopband in soliton speed exists. Solitons do not propagate in the stopband, although they can occur for both higher and lower speeds. The stopbands are associated with amore » limiting curve of the existence domain that is double-valued in speed for a range of values of f. Analytical estimates of the upper and lower limits of τ and μ that support stopbands are found. It is suggested that, inter alia, the analysis should be applicable to the solar wind plasma.« less

45 CFR 3.26 - Speed limit.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 45 Public Welfare 1 2012-10-01 2012-10-01 false Speed limit. 3.26 Section 3.26 Public Welfare DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL ADMINISTRATION CONDUCT OF PERSONS AND TRAFFIC ON THE NATIONAL INSTITUTES OF HEALTH FEDERAL ENCLAVE Traffic Regulations § 3.26 Speed limit. The speed limit is 25 miles per...

45 CFR 3.26 - Speed limit.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 45 Public Welfare 1 2014-10-01 2014-10-01 false Speed limit. 3.26 Section 3.26 Public Welfare Department of Health and Human Services GENERAL ADMINISTRATION CONDUCT OF PERSONS AND TRAFFIC ON THE NATIONAL INSTITUTES OF HEALTH FEDERAL ENCLAVE Traffic Regulations § 3.26 Speed limit. The speed limit is 25 miles per...

45 CFR 3.26 - Speed limit.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 45 Public Welfare 1 2013-10-01 2013-10-01 false Speed limit. 3.26 Section 3.26 Public Welfare DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL ADMINISTRATION CONDUCT OF PERSONS AND TRAFFIC ON THE NATIONAL INSTITUTES OF HEALTH FEDERAL ENCLAVE Traffic Regulations § 3.26 Speed limit. The speed limit is 25 miles per...

Maximum speed limits. Volume 3, A programmed implementation manual for setting a speed limit based on the 85th percentile

DOT National Transportation Integrated Search

1970-10-01

This report contains the implementation manual developed as a part of the project "Maximum Speed Limits." The manual consists of a programed educational unit and a field workguide concerning the setting of speed limits based on the 85th percentile sp...

14 CFR 25.33 - Propeller speed and pitch limits.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Propeller speed and pitch limits. 25.33... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight General § 25.33 Propeller speed and pitch limits. (a) The propeller speed and pitch must be limited to values that will ensure— (1) Safe operation...

14 CFR 29.1517 - Limiting height-speed envelope.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Limiting height-speed envelope. 29.1517... Operating Limitations § 29.1517 Limiting height-speed envelope. For Category A rotorcraft, if a range of heights exists at any speed, including zero, within which it is not possible to make a safe landing...

14 CFR 25.33 - Propeller speed and pitch limits.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Propeller speed and pitch limits. 25.33... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight General § 25.33 Propeller speed and pitch limits. (a) The propeller speed and pitch must be limited to values that will ensure- (1) Safe operation...

14 CFR 29.1517 - Limiting height-speed envelope.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Limiting height-speed envelope. 29.1517... Operating Limitations § 29.1517 Limiting height-speed envelope. For Category A rotorcraft, if a range of heights exists at any speed, including zero, within which it is not possible to make a safe landing...

LAVIA--an evaluation of the potential safety benefits of the French intelligent speed adaptation project.

PubMed

Driscoll, R; Page, Y; Lassarre, S; Ehrlich, J

2007-01-01

This paper presents the potential safety benefits of the experimental French LAVIA Intelligent Speed Adaptation system, according to road network and system mode, based on observed driving speeds, distributions of crash severity and crash injury risk. Results are given for car frontal and side impacts that together, represent 80% of all serious and fatal injuries in France. Of the three system modes tested (advisory, driver select, mandatory), our results suggest that driver select would most significantly reduce serious injuries and death. We estimate this 100% utilization of cars equipped with this type of speed adaptation system would decrease injury rates by 6% to 16% over existing conditions depending on the type of crash (frontal or side) and road environment considered. Some limitations associated with the analysis are also identified. LAVIA is the acronym for Limiteur s'Adaptant à la VItesse Autorisée, a French Intelligent Speed Adaptation (ISA) project that was set up towards the end of 1999. At the time, 1998 French national road safety statistics recorded 8437 road related deaths, a figure which had shown virtually no positive evolution since 1994. Detailed analysis of the contributory factors involved in fatal road crashes highlighted the time-honoured crash and injury causation mechanisms - alcohol, speed and seatbelts. Of the three, excessive speed (over and above the posted speed limit) was a contributory factor in half of all fatal crashes Inappropriate behaviour such as excessive speeding can be dealt with either by legislative or driver-incentive programmes. The first of these two solutions involves the introduction of new legislation and/or the enforcement of existing laws. This is the domain of Public Authorities and will not be discussed in detail here. Alternatively, incentive schemes can involve the implementation of speed related driver assistance systems, categorised according to their voluntary or mandatory character and the degree of autonomy proposed to or imposed on the driver. The LAVIA project set out to address several possible combinations of these two factors. The generic term Intelligent Speed Adaptation (ISA) encompasses a wide range of different technologies aimed at improving road safety by reducing traffic speed and homogenising traffic flow, within the limit of posted speed limits. "Fixed speed limit" systems inform the vehicle of the posted speed limit whereas "variable speed limit" systems take into account certain locations on the road network where a speed below the posted limit is desirable, such as sharp curves, pedestrian crossings or crash black spots. Taken one step further, speed limit systems may also take into account weather and traffic flow conditions. These systems are known as "dynamic speed limit" systems and benefit from real time updates for a specific location. The different ISA systems are generally characterised by the degree of freedom of choice given to the driver in moderating his or her speed. Speed limit technologies may be advisory (informing drivers of the current speed limit and speed limit changes), voluntary (allowing the driver to decide whether or not to implement speed limitation) or mandatory (imposing the current speed limit). The information supplied may be provided by way of the road infrastructure (and associated equipment), may be acquired autonomously by the vehicle or may be based on an interaction between the infrastructure and the vehicle. Even the most basic of these systems should be considered as a very useful driver aid, helping the driver to stay within the posted speed limit, avoiding "unnecessary" speeding fines through inattention, modelling driver behaviour through the long term reduction of speeds and reducing driver workload by limiting visual speedometer controls. Vehicle-based ISA systems should not be confused with internal systems. These latter systems rely upon the driver entering the desired travel speed, which is then maintained by cruise control or set as a maximum value by automatic speed regulators. Although these systems will not be discussed in detail here, it should be noted that the engine management technologies that they employ are a vital component of ISA systems.

Driving on urban roads: How we come to expect the 'correct' speed.

PubMed

Charlton, Samuel G; Starkey, Nicola J

2017-11-01

The subjective categories that drivers use to distinguish between different road types have been shown to influence the speeds they choose to drive but as yet we do not understand the road features that drivers use to make their discriminations. To better understand how drivers describe and categorise the roads they drive, 55 participants were recruited to drive a video of familiar urban roads in a driving simulator at the speed they would drive these roads in their own cars (using the accelerator and brake pedal in the driving simulator to adjust their speed). The participants were then asked to sort photos of the roads they had just driven into piles so that their driving would be the same on all roads in one pile but different to the other piles. Finally, they answered a series of questions about each road to indicate what speed they would drive, the safe speed for the road, their speed limit belief as well as providing ratings of comfort, difficulty and familiarity. Overall, drivers' categorisation of roads was informed by a number of factors including speed limit belief, road features and markings (including medians), road width, and presence of houses, driveways and footpaths. The participants' categories were congruent with what they thought the speed limits were, but not necessarily the actual speed limits. Mismatches between actual speed limits and speed limit beliefs appeared to result from category-level expectations about speed limits that took precedence over recent experience in the simulator. Roads that historically had a 50km/h speed limit but had been reduced to 40km/h were still regarded as 50km/h roads by the participants, underscoring the point that simply posting a sign with a lower speed limit is not enough to overcome drivers' expectations and habits associated with the visual appearance of a road. The findings provided insights into how drivers view and categorise roads, and identify specific areas that could be used to improve speed limit credibility. Copyright © 2017 Elsevier Ltd. All rights reserved.

Prevalence of drink driving and speeding in China: a time series analysis from two cities.

PubMed

Li, Q; He, H; Duan, L; Wang, Y; Bishai, D M; Hyder, A A

2017-03-01

To confront the public health challenge imposed by road traffic injuries in China. A consortium of international partners designed and implemented targeted interventions, such as social media campaigns, advocacy for legislative change and law enforcement training, to reduce the percentage of drink driving and speeding in two Chinese cities, Dalian and Suzhou, from 2010 to 2014. Time series models were developed to detect changes in the prevalence of drink driving and speeding using data collected through four years of observational studies. This analysis, based on 15 rounds of data, shows that from May 2011 to November 2014, the percentage of vehicles driving above the speed limit decreased from 31.8% (95% confidence interval [CI]: 29.2-34.5) to 7.4% (95% CI: 7.0-7.9) in Dalian and from 13.5% (95% CI: 11.7-15.5) to 6.9% (95% CI: 6.4-7.4) in Suzhou. Drink driving decreased from 1.7% (95% CI: 1.1-2.4) in January 2011 to 0.5% (95% CI: 0.2-0.9) in November 2014 in Dalian and from 6.4% (95% CI: 5.4-7.4) to 0.5% (95% CI: 0.1-2.4) in Suzhou during approximately the same period. Time series models confirmed declining trends in both risk factors in both cities (P-value: 0.06 for speeding prevalence in Suzhou; all other P-values are below 0.05). Disaggregated by vehicle type, saloon cars and SUVs were more likely to exceed the posted speed limit than other types of vehicles in both cities. The speeding rate was higher where the posted speed limit is lower. In Dalian, more drivers were driving above the posted speed limit on weekdays than on weekends (11.4% vs 6.8%); Suzhou had a similar pattern, but the difference was smaller (14.0% vs 12.2%). Despite the challenge in accurately attributing the observed changes to one programme, the substantial reduction in the prevalence of the two risk factors suggests that through coordinated actions, internationally recognized best practices in road safety may be effective in improving road traffic safety in China. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

[Spanish drivers' beliefs about speed. Speeding is a major issue of road safety].

PubMed

Montoro González, Luis; Roca Ruiz, Javier; Lucas-Alba, Antonio

2010-11-01

Extending and updating our knowledge concerning drivers' motivational and cognitive processes is of essential importance if we are to apply policies with long-lasting effects. This study presents data from a representative national survey analyzing the Spanish drivers' beliefs about speed, the risks of speeding, the degree of violation of speed-limits and the reasons for speeding. Results indicate that Spanish drivers rate speeding as a serious offence, yet not among the most dangerous ones. All in all, they claim to comply mostly with the speed limits. However, some interesting violation patterns emerge: observance is lower for generic speed limits according to road type (vs. specific limits shown by certain road signs), and particularly in motorways (vs. single carriageways and urban areas). Risk perception and reasons for speeding emerge as the main factors predicting the levels of speed violations reported. Results suggest that any effective intervention strategy should consider such factors, namely the link between speed, road safety, and drivers' specific reasons for speeding.

Maximum speed limits. Volume 4, An implementation method for setting a speed limit based on the 85th percentile speed

DOT National Transportation Integrated Search

1970-10-01

This volume contains an explanation of a method for setting a speed limit which was developed as a part of the project conducted by the Institute for Research in Public Safety under Contract No. FH-11-7275, "A Study for the Selection of Maximum Speed...

14 CFR 23.33 - Propeller speed and pitch limits.

Code of Federal Regulations, 2014 CFR

2014-01-01

... the all engine(s) operating climb speed specified in § 23.65, the propeller must limit the engine r.p... approved overspeed, a means to limit the maximum engine and propeller speed to not more than the maximum... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Propeller speed and pitch limits. 23.33...

14 CFR 23.33 - Propeller speed and pitch limits.

Code of Federal Regulations, 2013 CFR

2013-01-01

... the all engine(s) operating climb speed specified in § 23.65, the propeller must limit the engine r.p... approved overspeed, a means to limit the maximum engine and propeller speed to not more than the maximum... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Propeller speed and pitch limits. 23.33...

14 CFR 23.33 - Propeller speed and pitch limits.

Code of Federal Regulations, 2012 CFR

2012-01-01

... the all engine(s) operating climb speed specified in § 23.65, the propeller must limit the engine r.p... approved overspeed, a means to limit the maximum engine and propeller speed to not more than the maximum... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Propeller speed and pitch limits. 23.33...

Effective ion speeds at ˜200-250 km from comet 67P/Churyumov-Gerasimenko near perihelion

NASA Astrophysics Data System (ADS)

Vigren, E.; André, M.; Edberg, N. J. T.; Engelhardt, I. A. D.; Eriksson, A. I.; Galand, M.; Goetz, C.; Henri, P.; Heritier, K.; Johansson, F. L.; Nilsson, H.; Odelstad, E.; Rubin, M.; Stenberg-Wieser, G.; Tzou, C.-Y.; Vallières, X.

2017-07-01

In 2015 August, comet 67P/Churyumov-Gerasimenko, the target comet of the ESA Rosetta mission, reached its perihelion at ˜1.24 au. Here, we estimate for a three-day period near perihelion, effective ion speeds at distances ˜200-250 km from the nucleus. We utilize two different methods combining measurements from the Rosetta Plasma Consortium (RPC)/Mutual Impedance Probe with measurements either from the RPC/Langmuir Probe or from the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA)/Comet Pressure Sensor (COPS) (the latter method can only be applied to estimate the effective ion drift speed). The obtained ion speeds, typically in the range 2-8 km s-1, are markedly higher than the expected neutral outflow velocity of ˜1 km s-1. This indicates that the ions were de-coupled from the neutrals before reaching the spacecraft location and that they had undergone acceleration along electric fields, not necessarily limited to acceleration along ambipolar electric fields in the radial direction. For the limited time period studied, we see indications that at increasing distances from the nucleus, the fraction of the ions' kinetic energy associated with radial drift motion is decreasing.

Pedestrian fatality and impact speed squared: Cloglog modeling from French national data.

PubMed

Martin, Jean-Louis; Wu, Dan

2018-01-02

The present study estimates pedestrians' risk of death according to impact speed when hit by a passenger car in a frontal collision. Data were coded for all fatal crashes in France in 2011 and for a random sample of 1/20th of all road injuries for the same year and weighted to take into account police underreporting of mild injury. A cloglog model was used to optimize risk adjustment for high collision speeds. The fit of the model on the data was also improved by using the square of the impact speed, which best matches the energy dissipated in the collision. Modeling clearly demonstrated that the risk of death was very close to 1 when impact speeds exceeded 80 km/h. For speeds less than 40 km/h, because data representative of all crashes resulting in injury were used, the estimated risk of death was fairly low. However, although the curve seemed deceptively flat below 50 km/h, the risk of death in fact rose 2-fold between 30 and 40 km/h and 6-fold between 30 and 50 km/h. For any given speed, the risk of death was much higher for more elderly subjects, especially those over 75 years of age. These results concern frontal crashes involving a passenger car. Collisions involving trucks are far less frequent, but half result in the pedestrian being run over, incurring greater mortality. For impact speeds below 60 km/h, the shape of the curve relating probability of death to impact speed was very similar to those reported in recent rigorous studies. For higher impact speeds, the present model allows the curve to rise ever more steeply, giving a much better fit to observed data. The present results confirm that, when a pedestrian is struck by a car, impact speed is a major risk factor, thus providing a supplementary argument for strict speed limits in areas where pedestrians are highly exposed.

Speed limiter integrated fatigue analyzer (SLIFA) for speed and fatigue control on diesel engine truck and bus

NASA Astrophysics Data System (ADS)

Wahyudi, Haris; Pranoto, Hadi; Leman, A. M.; Sebayang, Darwin; Baba, I.

2017-09-01

Every second, the number of road traffic deaths is increased globally with millions more sustaining severe injuries and living with long-term adverse health consequences. Jakarta alone in year 2015 had recorded 556 people died due to road accidents, approximately reached 6.231 road accident cases. The identified major contributory factors of such unfortunate events are both driver fatigue and over speeding habit especially related to the driving of truck and bus. This paper presents the idea on how to control the electronic system from input fuel system of injection pump and the combustion chamber engine will control the valve solenoid in injection pump which can lock and fuel will stop for moment, and speed limit can be success, by using sensor heart rate we can input reduce speed limit when fatigue detection driver. Integration process this tool can be relevant when Speed Limiter Integrated Fatigue Analyser (SLIFA) trial in the diesel engine for truck and bus, the result of this research Speed Limiter Integrated Fatigue Analyser (SLIFA) able to control speed of diesel engine for truck and bus almost 30km/h, 60km/h, and until 70 km/h. The installation of the sensor heart rate as the input speed limit SLIFA would work when the driver is detected to be in the fatigue condition. We make Speed Limiter Integrated Fatigue Analyser (SLIFA) for control and monitoring system for diesel engine in truck and bus. Speed Limiter Integrated Fatigue Analyser (SLIFA) system can save the historical of the speed record, fatigue, rpm, and body temperature of the driver.

Safety impacts of differential speed limits on rural interstate highways

DOT National Transportation Integrated Search

2005-10-01

To compare the safety effects of a uniform speed limit (USL) for all vehicles as opposed to a differential speed limit (DSL) for cars and heavy trucks, detailed crash data, speed monitoring data, and traffic volumes were sought for rural interstate h...

System solution to improve energy efficiency of HVAC systems

NASA Astrophysics Data System (ADS)

Chretien, L.; Becerra, R.; Salts, N. P.; Groll, E. A.

2017-08-01

According to recent surveys, heating and air conditioning systems account for over 45% of the total energy usage in US households. Three main types of HVAC systems are available to homeowners: (1) fixed-speed systems, where the compressor cycles on and off to match the cooling load; (2) multi-speed (typically, two-speed) systems, where the compressor can operate at multiple cooling capacities, leading to reduced cycling; and (3) variable-speed systems, where the compressor speed is adjusted to match the cooling load of the household, thereby providing higher efficiency and comfort levels through better temperature and humidity control. While energy consumption could reduce significantly by adopting variable-speed compressor systems, the market penetration has been limited to less than 10% of the total HVAC units and a vast majority of systems installed in new construction remains single speed. A few reasons may explain this phenomenon such as the complexity of the electronic circuitry required to vary compressor speed as well as the associated system cost. This paper outlines a system solution to boost the Seasonal Energy Efficiency Rating (SEER) of a traditional single-speed unit through using a low power electronic converter that allows the compressor to operate at multiple low capacity settings and is disabled at high compressor speeds.

Nilsson's Power Model connecting speed and road trauma: applicability by road type and alternative models for urban roads.

PubMed

Cameron, M H; Elvik, R

2010-11-01

Nilsson (1981) proposed power relationships connecting changes in traffic speeds with changes in road crashes at various levels of injury severity. Increases in fatal crashes are related to the 4(th) power of the increase in mean speed, increases in serious casualty crashes (those involving death or serious injury) according to the 3(rd) power, and increases in casualty crashes (those involving death or any injury) according to the 2(nd) power. Increases in numbers of crash victims at cumulative levels of injury severity are related to the crash increases plus higher powers predicting the number of victims per crash. These relationships are frequently applied in OECD countries to estimate road trauma reductions resulting from expected speed reductions. The relationships were empirically derived based on speed changes resulting from a large number of rural speed limit changes in Sweden during 1967-1972. Nilsson (2004) noted that there had been very few urban speed limit changes studied to test his power model. This paper aims to test the assumption that the model is equally applicable in all road environments. It was found that the road environment is an important moderator of Nilsson's power model. While Nilsson's model appears satisfactory for rural highways and freeways, the model does not appear to be directly applicable to traffic speed changes on urban arterial roads. The evidence of monotonically increasing powers applicable to changes in road trauma at increasing injury severity levels with changes in mean speed is weak. The estimated power applicable to serious casualties on urban arterial roads was significantly less than that on rural highways, which was also significantly less than that on freeways. Alternative models linking the parameters of speed distributions with road trauma are reviewed and some conclusions reached for their use on urban roads instead of Nilsson's model. Further research is needed on the relationships between serious road trauma and urban speeds. 2010 Elsevier Ltd. All rights reserved.

Multi-epoch VLBA Imaging of 20 New TeV Blazars: Apparent Jet Speeds

NASA Astrophysics Data System (ADS)

Piner, B. Glenn; Edwards, Philip G.

2018-01-01

We present 88 multi-epoch Very Long Baseline Array (VLBA) images (most at an observing frequency of 8 GHz) of 20 TeV blazars, all of the high-frequency-peaked BL Lac (HBL) class, that have not been previously studied at multiple epochs on the parsec scale. From these 20 sources, we analyze the apparent speeds of 43 jet components that are all detected at four or more epochs. As has been found for other TeV HBLs, the apparent speeds of these components are relatively slow. About two-thirds of the components have an apparent speed that is consistent (within 2σ) with no motion, and some of these components may be stationary patterns whose apparent speed does not relate to the underlying bulk flow speed. In addition, a superluminal tail to the apparent speed distribution of the TeV HBLs is detected for the first time, with eight components in seven sources having a 2σ lower limit on the apparent speed exceeding 1c. We combine the data from these 20 sources with an additional 18 sources from the literature to analyze the complete apparent speed distribution of all 38 TeV HBLs that have been studied with very long baseline interferometry at multiple epochs. The highest 2σ apparent speed lower limit considering all sources is 3.6c. This suggests that bulk Lorentz factors of up to about 4, but probably not much higher, exist in the parsec-scale radio-emitting regions of these sources, consistent with estimates obtained in the radio by other means such as brightness temperatures. This can be reconciled with the high Lorentz factors estimated from the high-energy data if the jet has velocity structures consisting of different emission regions with different Lorentz factors. In particular, we analyze the current apparent speed data for the TeV HBLs in the context of a model with a fast central spine and a slower outer layer.

Speed limits of aircraft

NASA Technical Reports Server (NTRS)

Everling, E

1923-01-01

This paper is restricted to the question of attainable speed limits and attacks the problem from different angles. Theoretical limits due to air resistance are presented along with design factors which may affect speed such as wing loads, wing areas, wing section shifting, landing speeds, drag-lift ratios, and power coefficients.

Single software platform used for high speed data transfer implementation in a 65k pixel camera working in single photon counting mode

NASA Astrophysics Data System (ADS)

Maj, P.; Kasiński, K.; Gryboś, P.; Szczygieł, R.; Kozioł, A.

2015-12-01

Integrated circuits designed for specific applications generally use non-standard communication methods. Hybrid pixel detector readout electronics produces a huge amount of data as a result of number of frames per seconds. The data needs to be transmitted to a higher level system without limiting the ASIC's capabilities. Nowadays, the Camera Link interface is still one of the fastest communication methods, allowing transmission speeds up to 800 MB/s. In order to communicate between a higher level system and the ASIC with a dedicated protocol, an FPGA with dedicated code is required. The configuration data is received from the PC and written to the ASIC. At the same time, the same FPGA should be able to transmit the data from the ASIC to the PC at the very high speed. The camera should be an embedded system enabling autonomous operation and self-monitoring. In the presented solution, at least three different hardware platforms are used—FPGA, microprocessor with real-time operating system and the PC with end-user software. We present the use of a single software platform for high speed data transfer from 65k pixel camera to the personal computer.

Factors Influencing Injury Severity of Bicyclists Involved in Crashes with Motor Vehicles: Bike Lanes, Alcohol, Lighting, Speed, and Helmet Use.

PubMed

Helak, Kelsey; Jehle, Dietrich; McNabb, Daniel; Battisti, Amanda; Sanford, Steward; Lark, Mary Claire

2017-07-01

In 2014, 726 bicyclists were killed and an additional 50,000 were injured in crashes with motor vehicles. The number of cyclists in the United States is increasing, and as a result there has been a call for more bike lanes. We examined the difference in the severity of injury of bicyclists involved in motor vehicle crashes when riding in the traffic lane compared with riding in a bike lane or on a paved shoulder. We also controlled for other safety factors, including alcohol use, travel speed, posted speed, helmet usage, and lighting conditions to determine their impact on bicyclist safety. Single-year National Automotive Sampling System-General Estimates System files were used to analyze data regarding the bike lanes, and multiyear data were used to analyze the additional factors. Univariate and multiple regression analyses controlling for confounders were performed on the data. When adjusting for speed limit, alcohol use by driver, weather conditions, time of day, and helmet use, the cyclist's position had no significant effect on the severity of injury ( P = 0.57). The severity of injury was significantly greater when the driver or bicyclist had been drinking alcohol ( P < 0.0001 and P < 0.003, respectively). Bicyclists were more severely injured when vehicles moved at greater speeds and the posted speed limit was higher ( P < 0.0001 for both). Also, injury severity was found to be significantly higher when lighting conditions were "dark" ( P < 0.0001). Our findings suggest that simply having a dedicated space for bicyclists, such as a bike lane or a paved shoulder, does not reduce the severity of injuries sustained when a crash with a motor vehicle takes place. Cyclist safety could be improved by implementing changes that affect vehicle speed, alcohol use by drivers, and lighting conditions. Moreover, emergency physicians should be aware that when they receive a report of a cyclist being struck by a car in a bike lane, they should prepare to treat injuries of severity similar to those received by a bicyclist hit by a vehicle in traffic.

Cycling injury risk in London: A case-control study exploring the impact of cycle volumes, motor vehicle volumes, and road characteristics including speed limits.

PubMed

Aldred, Rachel; Goodman, Anna; Gulliver, John; Woodcock, James

2018-08-01

Cycling injury risk is an important topic, but few studies explore cycling risk in relation to exposure. This is largely because of a lack of exposure data, in other words how much cycling is done at different locations. This paper helps to fill this gap. It reports a case-control study of cycling injuries in London in 2013-2014, using modelled cyclist flow data alongside datasets covering some characteristics of the London route network. A multilevel binary logistic regression model is used to investigate factors associated with injury risk, comparing injury sites with control sites selected using the modelled flow data. Findings provide support for 'safety in numbers': for each increase of a natural logarithmic unit (2.71828) in cycling flows, an 18% decrease in injury odds was found. Conversely, increased motor traffic volume is associated with higher odds of cycling injury, with one logarithmic unit increase associated with a 31% increase in injury odds. Twenty-mile per hour compared with 30mph speed limits were associated with 21% lower injury odds. Residential streets were associated with reduced injury odds, and junctions with substantially higher injury odds. Bus lanes do not affect injury odds once other factors are controlled for. These data suggest that speed limits of 20 mph may reduce cycling injury risk, as may motor traffic reduction. Further, building cycle routes that generate new cycle trips should generate 'safety in numbers' benefits. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

Correlation of the Trim Limits of Stability Obtained for a PB2Y-3 Flying Boat and a 1/8-Size Powered Dynamic Model

NASA Technical Reports Server (NTRS)

Garrison, Charlie C.; Hacskaylo, Andrew

1947-01-01

Tests of a PB2Y-3 flying boat were made at the U.S> Naval Air Station, Patuxent River, Md., to determine its hydrodynamic trim limits of stability. Corresponding tests were also made of a 1/8-size powered dynamic model of the same flying boat in Langley tank no. 1. During the tank tests, the full-size testing procedure was reproduced as closely as possible in order to obtain data for a direct correlation of the results. As a nominal gross load of 66,000 pounds, the lower trim limits of the full-size and model were in good agreement above a speed of 80 feet per second. As the speed decreased below 80 feet per second, the difference between the model trim limits and full-scale trim limits gradually became larger. The upper trim limit of the model with flaps deflected 0 deg was higher than that of the full-size, but the difference was small over the speed range compared. At flap deflections greater than 0 deg, it was not possible to trim either the model of the airplane to the upper limit with the center of gravity at 28 percent of the mean aerodynamic chord. The decrease in the lower trim limits with increase in flap deflection showed good agreement for the airplane and model. The lower trim limits obtained at different gross loads for the full-size airplane were reduced to approximately a single curve by plotting trim against the square root of C(sub delta (sub o)) divided by C(sub V).

Volcanic Plume Heights on Mars: Limits of Validity for Convective Models

NASA Technical Reports Server (NTRS)

Glaze, Lori S.; Baloga, Stephen M.

2002-01-01

Previous studies have overestimated volcanic plume heights on Mars. In this work, we demonstrate that volcanic plume rise models, as currently formulated, have only limited validity in any environment. These limits are easily violated in the current Mars environment and may also be violated for terrestrial and early Mars conditions. We indicate some of the shortcomings of the model with emphasis on the limited applicability to current Mars conditions. Specifically, basic model assumptions are violated when (1) vertical velocities exceed the speed of sound, (2) radial expansion rates exceed the speed of sound, (3) radial expansion rates approach or exceed the vertical velocity, or (4) plume radius grossly exceeds plume height. All of these criteria are violated for the typical Mars example given here. Solutions imply that the convective rise, model is only valid to a height of approximately 10 kilometers. The reason for the model breakdown is hat the current Mars atmosphere is not of sufficient density to satisfy the conservation equations. It is likely that diffusion and other effects governed by higher-order differential equations are important within the first few kilometers of rise. When the same criteria are applied to eruptions into a higher-density early Mars atmosphere, we find that eruption rates higher than 1.4 x 10(exp 9) kilograms per second also violate model assumptions. This implies a maximum extent of approximately 65 kilometers for convective plumes on early Mars. The estimated plume heights for both current and early Mars are significantly lower than those previously predicted in the literature. Therefore, global-scale distribution of ash seems implausible.

Experimental and Numerical Study on Performance of Ducted Hydrokinetic Turbines with Pre-Swirl Stator Blades.

NASA Astrophysics Data System (ADS)

Gish, Andrew

2015-11-01

Ducts (also called shrouds) have been shown to improve performance of hydrokinetic turbines in some situations, bringing the power coefficient (Cp) closer to the Betz limit. Here we investigate optimization of the duct design as well as the addition of stator blades upstream of the turbine rotor to introduce pre-swirl in the flow. A small scale three-bladed turbine was tested in a towing tank. Three cases (bare turbine, with duct, and with duct and stators) were tested over a range of flow speeds. Important parameters include duct cross-sectional shape, blade-duct gap, stator cross-sectional shape, and stator angle. For each test, Cp was evaluated as a function of tip speed ratio (TSR). Experimental results were compared with numerical simulations. Results indicate that ducts and stators can improve performance at slower flow speeds and lower the stall speed compared to a bare turbine, but may degrade performance at higher speeds. Ongoing efforts to optimize duct and stator configurations will be discussed.

Lowering thresholds for speed limit enforcement impairs peripheral object detection and increases driver subjective workload.

PubMed

Bowden, Vanessa K; Loft, Shayne; Tatasciore, Monica; Visser, Troy A W

2017-01-01

Speed enforcement reduces incidences of speeding, thus reducing traffic accidents. Accordingly, it has been argued that stricter speed enforcement thresholds could further improve road safety. Effective speed monitoring however requires driver attention and effort, and human information-processing capacity is limited. Emphasizing speed monitoring may therefore reduce resource availability for other aspects of safe vehicle operation. We investigated whether lowering enforcement thresholds in a simulator setting would introduce further competition for limited cognitive and visual resources. Eighty-four young adult participants drove under conditions where they could be fined for travelling 1, 6, or 11km/h over a 50km/h speed-limit. Stricter speed enforcement led to greater subjective workload and significant decrements in peripheral object detection. These data indicate that the benefits of reduced speeding with stricter enforcement may be at least partially offset by greater mental demands on drivers, reducing their responses to safety-critical stimuli on the road. It is likely these results under-estimate the impact of stricter speed enforcement on real-world drivers who experience significantly greater pressures to drive at or above the speed limit. Copyright © 2016 Elsevier Ltd. All rights reserved.

Design guide for helicopter transmission seals

NASA Technical Reports Server (NTRS)

Hayden, T. S.; Keller, C. H., Jr.

1974-01-01

A detailed approach for the selection and design of seals for helicopter transmissions is presented. There are two major types of seals presently being used and they are lip type seals and mechanical type seals. Lip type seals can be divided in conventional lip seals and hydrodynamic lip seals. Conventional lip seals can be used for slow-speed, low-pressure, low-temperature sealing. Hydrodynamic lip seals although they are as pressure and temperature limited as conventional lip seals, can operate at a higher speed. Mechanical types seals are comprised of face seals and circumferential seals. Face seals are capable of high speed, high pressure, and high temperature. Circumferential seals can be used in high-speed and high-temperature applications, but will leak excessively at moderate pressures. The performance goals of transmission seals are a life that is at least equal to the scheduled overhaul interval of the gearbox component and a leakage rate of near zero.

Oxygen consumption, oxygen cost, heart rate, and perceived effort during split-belt treadmill walking in young healthy adults.

PubMed

Roper, Jaimie A; Stegemöller, Elizabeth L; Tillman, Mark D; Hass, Chris J

2013-03-01

During split-belt treadmill walking the speed of the treadmill under one limb is faster than the belt under the contralateral limb. This unique intervention has shown evidence of acutely improving gait impairments in individuals with neurologic impairment such as stroke and Parkinson's disease. However, oxygen use, heart rate and perceived effort associated with split-belt treadmill walking are unknown and may limit the utility of this locomotor intervention. To better understand the intensity of this new intervention, this study was undertaken to examine the oxygen consumption, oxygen cost, heart rate, and rating of perceived exertion associated with split-belt treadmill walking in young healthy adults. Fifteen participants completed three sessions of treadmill walking: slow speed with belts tied, fast speed with belts tied, and split-belt walking with one leg walking at the fast speed and one leg walking at the slow speed. Oxygen consumption, heart rate, and rating of perceived exertion were collected during each walking condition and oxygen cost was calculated. Results revealed that oxygen consumption, heart rate, and perceived effort associated with split-belt walking were higher than slow treadmill walking, but only oxygen consumption was significantly lower during both split-belt walking than fast treadmill walking. Oxygen cost associated with slow treadmill walking was significantly higher than fast treadmill walking. These findings have implications for using split-belt treadmill walking as a rehabilitation tool as the cost associated with split-belt treadmill walking may not be higher or potentially more detrimental than that associated with previously used treadmill training rehabilitation strategies.

Flame propagation in heterogeneous mixtures of fuel drops and air

NASA Technical Reports Server (NTRS)

Myers, G. D.; Lefebvre, A. H.

1984-01-01

Photographic methods are used to measure flame speeds in flowing mixtures of fuel props and air at atmospheric pressure. The fuels employed include a conventional fuel oil plus various blends JP 7 with stocks containing single-ring and mullti-ring aromatics. The results for stoichiometric mixtures show that flame propagation cannot occur in mixtures containing mean drop sizes larger than 300 to 400 microns, depending on the fuel type. For smaller drop sizes, down to around 60 microns, flame speed is inversely proportional to drop size, indicating that evaporation rates are limiting to flame speed. Below around 60 microns, the curves of flame speed versus mean drop size flatten out, thereby demonstrating that for finely atomized sprays flame speeds are much less dependent on evaporation rates, and are governed primarily by mixing and/or chemical reaction rates. The fuels exhibiting the highest flame speeds are those containing multi-ring aromatics. This is attributed to the higher radiative heat flux emanating from their soot-bearing flames which enhances the rate of evaporation of the fuel drops approaching the flame front.

Pulse-burst PIV in a high-speed wind tunnel

NASA Astrophysics Data System (ADS)

Beresh, Steven; Kearney, Sean; Wagner, Justin; Guildenbecher, Daniel; Henfling, John; Spillers, Russell; Pruett, Brian; Jiang, Naibo; Slipchenko, Mikhail; Mance, Jason; Roy, Sukesh

2015-09-01

Time-resolved particle image velocimetry (TR-PIV) has been achieved in a high-speed wind tunnel, providing velocity field movies of compressible turbulence events. The requirements of high-speed flows demand greater energy at faster pulse rates than possible with the TR-PIV systems developed for low-speed flows. This has been realized using a pulse-burst laser to obtain movies at up to 50 kHz, with higher speeds possible at the cost of spatial resolution. The constraints imposed by use of a pulse-burst laser are limited burst duration of 10.2 ms and a low duty cycle for data acquisition. Pulse-burst PIV has been demonstrated in a supersonic jet exhausting into a transonic crossflow and in transonic flow over a rectangular cavity. The velocity field sequences reveal the passage of turbulent structures and can be used to find velocity power spectra at every point in the field, providing spatial distributions of acoustic modes. The present work represents the first use of TR-PIV in a high-speed ground-test facility.

Process stability during fiber laser-arc hybrid welding of thick steel plates

NASA Astrophysics Data System (ADS)

Bunaziv, Ivan; Frostevarg, Jan; Akselsen, Odd M.; Kaplan, Alexander F. H.

2018-03-01

Thick steel plates are frequently used in shipbuilding, pipelines and other related heavy industries, and are usually joined by arc welding. Deep penetration laser-arc hybrid welding could increase productivity but has not been thoroughly investigated, and is therefore usually limited to applications with medium thickness (5-15 mm) sections. A major concern is process stability, especially when using modern welding consumables such as metal-cored wire and advanced welding equipment. High speed imaging allows direct observation of the process so that process behavior and phenomena can be studied. In this paper, 45 mm thick high strength steel was welded (butt joint double-sided) using the fiber laser-MAG hybrid process utilizing a metal-cored wire without pre-heating. Process stability was monitored under a wide range of welding parameters. It was found that the technique can be used successfully to weld thick sections with appropriate quality when the parameters are optimized. When comparing conventional pulsed and the more advanced cold metal transfer pulse (CMT+P) arc modes, it was found that both can provide high quality welds. CMT+P arc mode can provide more stable droplet transfer over a limited range of travel speeds. At higher travel speeds, an unstable metal transfer mechanism was observed. Comparing leading arc and trailing arc arrangements, the leading arc configuration can provide higher quality welds and more stable processing at longer inter-distances between the heat sources.

Effects on speed and safety of point-to-point speed enforcement systems: evaluation on the urban motorway A56 Tangenziale di Napoli.

PubMed

Montella, Alfonso; Imbriani, Lella Liana; Marzano, Vittorio; Mauriello, Filomena

2015-02-01

In this paper, we evaluated the effects on speed and safety of the point-to-point (P2P) speed enforcement system activated on the urban motorway A56 in Italy. The P2P speed enforcement is a relatively new approach to traffic law enforcement that involves the calculation of the average speed over a section. To evaluate the speed effects, we performed a before-after analysis of speed data investigating also effects on non-compliance to speed limits. To evaluate the safety effects, we carried out an empirical Bayes observational before-and-after study. The P2P system led to very positive effects on both speed and safety. As far as the effects on the section average travel speeds, the system yielded to a reduction in the mean speed, the 85th percentile speed, the standard deviation of speed, and the proportion of drivers exceeding the speed limits, exceeding the speed limits more than 10km/h, and exceeding the speed limits more than 20km/h. The best results were the decrease of the speed variability and the reduction of the excessive speeding behaviour. The decrease in the standard deviation of speed was 26% while the proportion of light and heavy vehicles exceeding the speed limits more than 20km/h was reduced respectively by 84 and 77%. As far as the safety effects, the P2P system yielded to a 32% reduction in the total crashes, with a lower 95% confidence limit of the estimate equal to 22%. The greatest crash reductions were in rainy weather (57%), on wet pavement (51%), on curves (49%), for single vehicle crashes (44%), and for injury crashes (37%). It is noteworthy that the system produced a statistically significant reduction of 21% in total crashes also in the part of the motorway where it was not activated, thus generating a significant spillover effect. The investigation of the effects of the P2P system on speed and safety over time allowed to develop crash modification functions where the relationship between crash modification factors and speed parameters (mean speed, 85th percentile speed, and standard deviation of speed) was expressed by a power function. Crash modification functions show that the effect of speed on safety is greater on curves and for injury crashes. Even though the study results show excellent outcomes, we must point out that the crash reduction effects decreased over time and speed, speed variability, and non-compliance to speed limits significantly increased over time. To maintain its effectiveness over time, P2P speed enforcement must be actively managed, i.e. constantly monitored and supported by appropriate sanctions. Copyright © 2014 Elsevier Ltd. All rights reserved.

Acceleration of low-energy ions at parallel shocks with a focused transport model

DOE PAGES

Zuo, Pingbing; Zhang, Ming; Rassoul, Hamid K.

2013-04-10

Here, we present a test particle simulation on the injection and acceleration of low-energy suprathermal particles by parallel shocks with a focused transport model. The focused transport equation contains all necessary physics of shock acceleration, but avoids the limitation of diffusive shock acceleration (DSA) that requires a small pitch angle anisotropy. This simulation verifies that the particles with speeds of a fraction of to a few times the shock speed can indeed be directly injected and accelerated into the DSA regime by parallel shocks. At higher energies starting from a few times the shock speed, the energy spectrum of acceleratedmore » particles is a power law with the same spectral index as the solution of standard DSA theory, although the particles are highly anisotropic in the upstream region. The intensity, however, is different from that predicted by DSA theory, indicating a different level of injection efficiency. It is found that the shock strength, the injection speed, and the intensity of an electric cross-shock potential (CSP) jump can affect the injection efficiency of the low-energy particles. A stronger shock has a higher injection efficiency. In addition, if the speed of injected particles is above a few times the shock speed, the produced power-law spectrum is consistent with the prediction of standard DSA theory in both its intensity and spectrum index with an injection efficiency of 1. CSP can increase the injection efficiency through direct particle reflection back upstream, but it has little effect on the energetic particle acceleration once the speed of injected particles is beyond a few times the shock speed. This test particle simulation proves that the focused transport theory is an extension of DSA theory with the capability of predicting the efficiency of particle injection.« less

15 CFR 265.12 - Speeding or reckless driving.

Code of Federal Regulations, 2014 CFR

2014-01-01

... of traffic, weather, and road surface and having regard to the actual and potential hazards existing...) of this section, the speed limit on the site is 25 m.p.h., unless another speed limit has been duly posted, and no person shall drive a motor vehicle on the site in excess of the speed limit. ...

15 CFR 265.12 - Speeding or reckless driving.

Code of Federal Regulations, 2012 CFR

2012-01-01

... of traffic, weather, and road surface and having regard to the actual and potential hazards existing...) of this section, the speed limit on the site is 25 m.p.h., unless another speed limit has been duly posted, and no person shall drive a motor vehicle on the site in excess of the speed limit. ...

15 CFR 265.12 - Speeding or reckless driving.

Code of Federal Regulations, 2013 CFR

2013-01-01

... of traffic, weather, and road surface and having regard to the actual and potential hazards existing...) of this section, the speed limit on the site is 25 m.p.h., unless another speed limit has been duly posted, and no person shall drive a motor vehicle on the site in excess of the speed limit. ...

15 CFR 265.12 - Speeding or reckless driving.

Code of Federal Regulations, 2011 CFR

2011-01-01

... of traffic, weather, and road surface and having regard to the actual and potential hazards existing...) of this section, the speed limit on the site is 25 m.p.h., unless another speed limit has been duly posted, and no person shall drive a motor vehicle on the site in excess of the speed limit. ...

36 CFR 4.21 - Speed limits.

Code of Federal Regulations, 2012 CFR

2012-07-01

... park road. Signs indicating that vehicle speed is determined by the use of radiomicrowaves or other... of park road under repair or construction. (3) 45 miles per hour: upon all other park roads. (b) The superintendent may designate a different speed limit upon any park road when a speed limit set forth in paragraph...

36 CFR 4.21 - Speed limits.

Code of Federal Regulations, 2014 CFR

2014-07-01

... park road. Signs indicating that vehicle speed is determined by the use of radiomicrowaves or other... of park road under repair or construction. (3) 45 miles per hour: upon all other park roads. (b) The superintendent may designate a different speed limit upon any park road when a speed limit set forth in paragraph...

36 CFR 4.21 - Speed limits.

Code of Federal Regulations, 2013 CFR

2013-07-01

... park road. Signs indicating that vehicle speed is determined by the use of radiomicrowaves or other... of park road under repair or construction. (3) 45 miles per hour: upon all other park roads. (b) The superintendent may designate a different speed limit upon any park road when a speed limit set forth in paragraph...

36 CFR 4.21 - Speed limits.

Code of Federal Regulations, 2011 CFR

2011-07-01

... park road. Signs indicating that vehicle speed is determined by the use of radiomicrowaves or other... of park road under repair or construction. (3) 45 miles per hour: upon all other park roads. (b) The superintendent may designate a different speed limit upon any park road when a speed limit set forth in paragraph...

36 CFR 4.21 - Speed limits.

Code of Federal Regulations, 2010 CFR

2010-07-01

... park road. Signs indicating that vehicle speed is determined by the use of radiomicrowaves or other... of park road under repair or construction. (3) 45 miles per hour: upon all other park roads. (b) The superintendent may designate a different speed limit upon any park road when a speed limit set forth in paragraph...

33 CFR 401.28 - Speed limits.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 33 Navigation and Navigable Waters 3 2011-07-01 2011-07-01 false Speed limits. 401.28 Section 401... TRANSPORTATION SEAWAY REGULATIONS AND RULES Regulations Seaway Navigation § 401.28 Speed limits. (a) The maximum speed over the bottom for a vessel of more than 12 m in overall length shall be regulated so as not to...

49 CFR 213.57 - Curves; elevation and speed limitations.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 4 2010-10-01 2010-10-01 false Curves; elevation and speed limitations. 213.57... speed limitations. (a) The maximum crosslevel on the outside rail of a curve may not be more than 8... applicable September 21, 1999.) (b)(1) The maximum allowable operating speed for each curve is determined by...

49 CFR 392.6 - Schedules to conform with speed limits.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 5 2010-10-01 2010-10-01 false Schedules to conform with speed limits. 392.6... DRIVING OF COMMERCIAL MOTOR VEHICLES General § 392.6 Schedules to conform with speed limits. No motor... points in such period of time as would necessitate the commercial motor vehicle being operated at speeds...

49 CFR 213.57 - Curves; elevation and speed limitations.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 4 2011-10-01 2011-10-01 false Curves; elevation and speed limitations. 213.57... speed limitations. (a) The maximum crosslevel on the outside rail of a curve may not be more than 8... applicable September 21, 1999.) (b)(1) The maximum allowable operating speed for each curve is determined by...

49 CFR 392.6 - Schedules to conform with speed limits.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 5 2011-10-01 2011-10-01 false Schedules to conform with speed limits. 392.6... DRIVING OF COMMERCIAL MOTOR VEHICLES General § 392.6 Schedules to conform with speed limits. No motor... points in such period of time as would necessitate the commercial motor vehicle being operated at speeds...

33 CFR 401.28 - Speed limits.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 33 Navigation and Navigable Waters 3 2010-07-01 2010-07-01 false Speed limits. 401.28 Section 401... TRANSPORTATION SEAWAY REGULATIONS AND RULES Regulations Seaway Navigation § 401.28 Speed limits. (a) The maximum speed over the bottom for a vessel of more than 12 m in overall length shall be regulated so as not to...

European birds adjust their flight initiation distance to road speed limits.

PubMed

Legagneux, Pierre; Ducatez, Simon

2013-10-23

Behavioural responses can help species persist in habitats modified by humans. Roads and traffic greatly affect animals' mortality not only through habitat structure modifications but also through direct mortality owing to collisions. Although species are known to differ in their sensitivity to the risk of collision, whether individuals can change their behaviour in response to this is still unknown. Here, we tested whether common European birds changed their flight initiation distances (FIDs) in response to vehicles according to road speed limit (a known factor affecting killing rates on roads) and vehicle speed. We found that FID increased with speed limit, although vehicle speed had no effect. This suggests that birds adjust their flight distance to speed limit, which may reduce collision risks and decrease mortality maximizing the time allocated to foraging behaviours. Mobility and territory size are likely to affect an individuals' ability to respond adaptively to local speed limits.

Systolic and Diastolic Blood Pressure, Incident Cardiovascular Events and Death in Elderly Persons: The Role of Functional Limitation in the Cardiovascular Health Study

PubMed Central

Peralta, Carmen A.; Katz, Ronit; Newman, Anne B.; Psaty, Bruce M.; Odden, Michelle C.

2014-01-01

Whether limitation in ability to perform activities of daily living (ADL) or gait speed can identify elders in whom the association of systolic (SBP) and diastolic (DBP) blood pressure with cardiovascular events (CVD) and death differs is unclear. We evaluated whether limitation in ADL or gait speed modify the association of SBP or DBP with incident CVD (N= 2,358) and death (N=3,547) in the Cardiovascular Health Study. Mean age was 78 ± 5 and 21% reported limitation in ≥1 ADL. There were 778 CV events and 1,289 deaths over 9 years. Among persons without and with ADL limitation, SBP was associated with incident CVD: HR (per 10 mmHg increase) 1.08 (95% CI 1.03, 1.13) and 1.06 (0.97, 1.17), respectively. ADL modified the association of DBP with incident CVD. Among those without ADL limitation, DBP was weakly associated with incident CVD, HR 1.04 (0.79, 1.37) for DBP > 80, compared with <65 mmHg. Among those with ADL limitation, DBP was inversely associated with CVD: HR 0.65 (0.44, 0.96) for DBP 66–80 mmHg and HR 0.49 (0.25, 0.94) for DBP > 80, compared to DBP ≤ 65. Among persons with ADL limitation, a DBP 66–80 had the lowest risk for death, HR 0.72 (0.57, 0.91), compared with DBP ≤ 65. Associations did not vary by 15 feet walking speed ADL can identify elders in whom diastolic hypotension is associated with higher CV risk and death. Functional status, rather than chronologic age alone, should inform design of hypertension trials in elders. PMID:24935945

Single-mode temperature and polarisation-stable high-speed 850nm vertical cavity surface emitting lasers

NASA Astrophysics Data System (ADS)

Nazaruk, D. E.; Blokhin, S. A.; Maleev, N. A.; Bobrov, M. A.; Kuzmenkov, A. G.; Vasil'ev, A. P.; Gladyshev, A. G.; Pavlov, M. M.; Blokhin, A. A.; Kulagina, M. M.; Vashanova, K. A.; Zadiranov, Yu M.; Fefelov, A. G.; Ustinov, V. M.

2014-12-01

A new intracavity-contacted design to realize temperature and polarization-stable high-speed single-mode 850 nm vertical cavity surface emitting lasers (VCSELs) grown by molecular-beam epitaxy is proposed. Temperature dependences of static and dynamic characteristics of the 4.5 pm oxide aperture InGaAlAs VCSEL were investigated in detail. Due to optimal gain-cavity detuning and enhanced carrier localization in the active region the threshold current remains below 0.75 mA for the temperature range within 20-90°C, while the output power exceeds 1 mW up to 90°C. Single-mode operation with side-mode suppression ratio higher than 30 dB and orthogonal polarization suppression ratio more than 18 dB was obtained in the whole current and temperature operation range. Device demonstrates serial resistance less than 250 Ohm, which is rather low for any type of single-mode short- wavelength VCSELs. VCSEL demonstrates temperature robust high-speed operation with modulation bandwidth higher than 13 GHz in the entire temperature range of 20-90°C. Despite high resonance frequency the high-speed performance of developed VCSELs was limited by the cut-off frequency of the parasitic low pass filter created by device resistances and capacitances. The proposed design is promising for single-mode high-speed VCSEL applications in a wide spectral range.

Forgetting induced speeding: Can prospective memory failure account for drivers exceeding the speed limit?

PubMed

Bowden, Vanessa K; Visser, Troy A W; Loft, Shayne

2017-06-01

It is generally assumed that drivers speed intentionally because of factors such as frustration with the speed limit or general impatience. The current study examined whether speeding following an interruption could be better explained by unintentional prospective memory (PM) failure. In these situations, interrupting drivers may create a PM task, with speeding the result of drivers forgetting their newly encoded intention to travel at a lower speed after interruption. Across 3 simulated driving experiments, corrected or uncorrected speeding in recently reduced speed zones (from 70 km/h to 40 km/h) increased on average from 8% when uninterrupted to 33% when interrupted. Conversely, the probability that participants traveled under their new speed limit in recently increased speed zones (from 40 km/h to 70 km/h) increased from 1% when uninterrupted to 23% when interrupted. Consistent with a PM explanation, this indicates that interruptions lead to a general failure to follow changed speed limits, not just to increased speeding. Further testing a PM explanation, Experiments 2 and 3 manipulated variables expected to influence the probability of PM failures and subsequent speeding after interruptions. Experiment 2 showed that performing a cognitively demanding task during the interruption, when compared with unfilled interruptions, increased the probability of initially speeding from 1% to 11%, but that participants were able to correct (reduce) their speed. In Experiment 3, providing participants with 10s longer to encode the new speed limit before interruption decreased the probability of uncorrected speeding after an unfilled interruption from 30% to 20%. Theoretical implications and implications for road design interventions are discussed. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Effects of transverse rumble strips on safety of pedestrian crosswalks on rural roads in China.

PubMed

Liu, Pan; Huang, Jia; Wang, Wei; Xu, Chengcheng

2011-11-01

The primary objective of this study is to evaluate the impacts of transverse rumble strips in reducing crashes and vehicle speeds at pedestrian crosswalks on rural roads in China. Using crash data reported at 366 sites, the research team conducted an observational before-after study using a comparison group and the Empirical Bayesian (EB) method to evaluate the effectiveness of transverse rumble strips in reducing crashes at pedestrian crosswalks. It was found that transverse rumble strips may reduce expected crash frequency at pedestrian crosswalks by 25%. The research team collected more than 15,000 speed observations at 12 sites. The speed data analysis results show that transverse rumble strips significantly reduce vehicle speeds in vicinity of pedestrian crosswalks on rural roads with posted speed limits of 60 km/h and 80 km/h. On average, the mean speed at pedestrian crosswalks declined 9.2 km/h on roads with a speed limit of 60 km/h; and 11.9 km/h on roads with a speed limit of 80 km/h. The 85th percentile speed declined 9.1 km/h on roads with a speed limit of 60 km/h; and 12.0 km/h on roads with a speed limit of 80 km/h. However, the speed reduction impacts were not found to be statistically significant for the pedestrian crosswalk on the road with a speed limit of 40 km/h. The study also looked extensively at the influence area of transverse rumble strips on rural roads. Speed profiles developed in this study show that the influence area of transverse rumble strips is generally less than 0.3 km. Copyright © 2011 Elsevier Ltd. All rights reserved.

Exceeding the speed limit: prevalence and determinants in Iran.

PubMed

Moradi, Ali; Motevalian, Seyed Abbas; Mirkoohi, Maryam; McKay, Mary Pat; Rahimi-Movaghar, Vafa

2013-01-01

Speeding is one of the most common risk behaviours associated with crashes causing signficant injury. The objective of this study is to explore the prevalence and determinants of speeding on a road between Tehran and Hamadan, Iran. In a cross-sectional study in 2009, stretches of the road were studied including three groups of posted speed limits: < 50 km/h, 50-100 km/h and > 100 km/h. Each stretch was evaluated both in daylight and dark. Randomly identified driver's speed was checked by a handheld speed camera and then the driver was invited to participate in a survey. Statistical analysis was performed using Chi-Square, crude and adjusted odds ratio, 95% confidence interval and multiple logistic regression models. Overall, 52.8% of the drivers were travelling more than 10 km/h above the posted limit. Where limits were < 50 km/h, 74.6% of drivers were speeding. This declined to 46.9% for sections with limits between 50 and 100 km/h and to 36.9% for sections posted more than 100 km/h. Finally, more than half the drivers were observed to be speeding. Driving more than the posted limit was far more likely on the areas with the lowest posted speed limits, personal passenger vehicles, modern vehicles not using seat belts, and male drivers.

14 CFR 23.1507 - Operating maneuvering speed.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Operating maneuvering speed. 23.1507... Limitations and Information § 23.1507 Operating maneuvering speed. The maximum operating maneuvering speed, VO, must be established as an operating limitation. VO is a selected speed that is not greater than VS√n...

14 CFR 23.1507 - Operating maneuvering speed.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Operating maneuvering speed. 23.1507... Limitations and Information § 23.1507 Operating maneuvering speed. The maximum operating maneuvering speed, VO, must be established as an operating limitation. VO is a selected speed that is not greater than VS√n...

Improvement in the light sensitivity of the ultrahigh-speed high-sensitivity CCD with a microlens array

NASA Astrophysics Data System (ADS)

Hayashida, T.,; Yonai, J.; Kitamura, K.; Arai, T.; Kurita, T.; Tanioka, K.; Maruyama, H.; Etoh, T. Goji; Kitagawa, S.; Hatade, K.; Yamaguchi, T.; Takeuchi, H.; Iida, K.

2008-02-01

We are advancing the development of ultrahigh-speed, high-sensitivity CCDs for broadcast use that are capable of capturing smooth slow-motion videos in vivid colors even where lighting is limited, such as at professional baseball games played at night. We have already developed a 300,000 pixel, ultrahigh-speed CCD, and a single CCD color camera that has been used for sports broadcasts and science programs using this CCD. However, there are cases where even higher sensitivity is required, such as when using a telephoto lens during a baseball broadcast or a high-magnification microscope during science programs. This paper provides a summary of our experimental development aimed at further increasing the sensitivity of CCDs using the light-collecting effects of a microlens array.

Variable Speed Limit (VSL) - Best Management Practice [Summary

DOT National Transportation Integrated Search

2012-01-01

In variable speed limit (VSL) zones, the speed : limit changes in response to traffic congestion, : adverse weather, or road conditions. VSL zones are : often highly automated and have been employed : successfully in several U.S. and European : locat...

Extending the process limits of laser polymer welding with high-brilliance beam sources (recent status and prospects of POLYBRIGHT)

NASA Astrophysics Data System (ADS)

Olowinsky, A.; Boglea, A.

2011-03-01

Plastics play an important role in almost every facet of our lives and constitute a wide variety of products, from everyday products such as food and beverage packaging, over furniture and building materials to high tech products in the automotive, electronics, aerospace, white goods, medical and other sectors [1]. The objective of PolyBright, the European Research project on laser polymer welding, is to provide high speed and flexible laser manufacturing technology and expand the limits of current plastic part assembly. New laser polymer joining processes for optimized thermal management in combination with adapted wavelengths will provide higher quality, high processing speed up to 1 m/s and robust manufacturing processes at lower costs. Key innovations of the PolyBright project are fibre lasers with high powers up to 500 W, high speed scanning and flexible beam manipulation systems for simultaneous welding and high-resolution welding, such as dynamic masks and multi kHz scanning heads. With this initial step, PolyBright will break new paths in processing of advanced plastic products overcoming the quality and speed limitations of conventional plastic part assembly. Completely new concepts for high speed processing, flexibility and quality need to be established in combination with high brilliance lasers and related equipment. PolyBright will thus open new markets for laser systems with a short term potential of over several 100 laser installations per year and a future much larger market share in the still growing plastic market. PolyBright will hence establish a comprehensive and sustainable development activity on new high brilliance lasers that will strengthen the laser system industry.

Two-photon polymerization as a structuring technology in production: future or fiction?

NASA Astrophysics Data System (ADS)

Harnisch, Emely Marie; Schmitt, Robert

2017-02-01

Two-photon polymerization (TPP) has become an established generative fabrication technique for individual, up to three-dimensional micro- and nanostructures. Due to its high resolution beyond the diffraction limit, its writing speed is limited and in most cases, very special structures are fabricated in small quantities. With regard to the trends of the optical market towards higher efficiencies, miniaturization and higher functionalities, there is a high demand for so called intelligent light management systems, including also individual optical elements. Here, TPP could offer a fabrication technique, enabling higher complexities of structures than conventional cutting and lithographic technologies do. But how can TPP opened up for production? In the following, some approaches to establish TPP as a mastering technique for molding are presented against this background.

Optical-domain subsampling for data efficient depth ranging in Fourier-domain optical coherence tomography

PubMed Central

Siddiqui, Meena; Vakoc, Benjamin J.

2012-01-01

Recent advances in optical coherence tomography (OCT) have led to higher-speed sources that support imaging over longer depth ranges. Limitations in the bandwidth of state-of-the-art acquisition electronics, however, prevent adoption of these advances into the clinical applications. Here, we introduce optical-domain subsampling as a method for imaging at high-speeds and over extended depth ranges but with a lower acquisition bandwidth than that required using conventional approaches. Optically subsampled laser sources utilize a discrete set of wavelengths to alias fringe signals along an extended depth range into a bandwidth limited frequency window. By detecting the complex fringe signals and under the assumption of a depth-constrained signal, optical-domain subsampling enables recovery of the depth-resolved scattering signal without overlapping artifacts from this bandwidth-limited window. We highlight key principles behind optical-domain subsampled imaging, and demonstrate this principle experimentally using a polygon-filter based swept-source laser that includes an intra-cavity Fabry-Perot (FP) etalon. PMID:23038343

49 CFR 213.9 - Classes of track: operating speed limits.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 4 2010-10-01 2010-10-01 false Classes of track: operating speed limits. 213.9... speed limits. (a) Except as provided in paragraph (b) of this section and §§ 213.57(b), 213.59(a), 213.113(a), and 213.137(b) and (c), the following maximum allowable operating speeds apply— [In miles per...

49 CFR 213.9 - Classes of track: operating speed limits.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 4 2011-10-01 2011-10-01 false Classes of track: operating speed limits. 213.9... speed limits. (a) Except as provided in paragraph (b) of this section and §§ 213.57(b), 213.59(a), 213.113(a), and 213.137(b) and (c), the following maximum allowable operating speeds apply— [In miles per...

14 CFR 25.33 - Propeller speed and pitch limits.

Code of Federal Regulations, 2012 CFR

2012-01-01

... used to limit the low pitch position of the propeller blades must be set so that the engine does not... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Propeller speed and pitch limits. 25.33... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight General § 25.33 Propeller speed and pitch limits...

14 CFR 25.33 - Propeller speed and pitch limits.

Code of Federal Regulations, 2014 CFR

2014-01-01

... used to limit the low pitch position of the propeller blades must be set so that the engine does not... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Propeller speed and pitch limits. 25.33... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight General § 25.33 Propeller speed and pitch limits...

14 CFR 25.33 - Propeller speed and pitch limits.

Code of Federal Regulations, 2013 CFR

2013-01-01

... used to limit the low pitch position of the propeller blades must be set so that the engine does not... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Propeller speed and pitch limits. 25.33... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight General § 25.33 Propeller speed and pitch limits...

Speed limits set lower than engineering recommendations : project summary report.

DOT National Transportation Integrated Search

2016-08-01

The Montana Department of Transportation (MDT) generally ensures that posted speed limits are set in accordance with engineering recommendations, which means that speed limits are typically set such that they are about equal to the observed 85th-perc...

Predictors of Change in Physical Function in Older Adults in Response to Long-Term, Structured Physical Activity: The LIFE Study.

PubMed

Layne, Andrew S; Hsu, Fang-Chi; Blair, Steven N; Chen, Shyh-Huei; Dungan, Jennifer; Fielding, Roger A; Glynn, Nancy W; Hajduk, Alexandra M; King, Abby C; Manini, Todd M; Marsh, Anthony P; Pahor, Marco; Pellegrini, Christine A; Buford, Thomas W

2017-01-01

To evaluate the extent of variability in functional responses in participants in the Lifestyle Interventions and Independence for Elders (LIFE) study and to identify the relative contributions of intervention adherence, physical activity, and demographic and health characteristics to this variability. Secondary analysis. Multicenter institutions. A volunteer sample (N=1635) of sedentary men and women aged 70 to 89 years who were able to walk 400m but had physical limitations, defined as a Short Physical Performance Battery (SPPB) score of ≤9. Moderate-intensity physical activity (n=818) consisting of aerobic, resistance, and flexibility exercises performed both center-based (2times/wk) and home-based (3-4times/wk) sessions or health education program (n=817) consisting of weekly to monthly workshops covering relevant health information. Physical function (gait speed over 400m) and lower extremity function (SPPB score) assessed at baseline and 6, 12, and 24 months. Greater baseline physical function (gait speed, SPPB score) was negatively associated with change in gait speed (regression coefficient β=-.185; P<.001) and change in SPPB score (β=-.365; P<.001), whereas higher number of steps per day measured by accelerometry was positively associated with change in gait speed (β=.035; P<.001) and change in SPPB score (β=.525; P<.001). Other baseline factors associated with positive change in gait speed and/or SPPB score include younger age (P<.001), lower body mass index (P<.001), and higher self-reported physical activity (P=.002). Several demographic and physical activity-related factors were associated with the extent of change in functional outcomes in participants in the LIFE study. These factors should be considered when designing interventions for improving physical function in older adults with limited mobility. Copyright © 2016 American Congress of Rehabilitation Medicine. All rights reserved.

Analyses of rear-end crashes based on classification tree models.

PubMed

Yan, Xuedong; Radwan, Essam

2006-09-01

Signalized intersections are accident-prone areas especially for rear-end crashes due to the fact that the diversity of the braking behaviors of drivers increases during the signal change. The objective of this article is to improve knowledge of the relationship between rear-end crashes occurring at signalized intersections and a series of potential traffic risk factors classified by driver characteristics, environments, and vehicle types. Based on the 2001 Florida crash database, the classification tree method and Quasi-induced exposure concept were used to perform the statistical analysis. Two binary classification tree models were developed in this study. One was used for the crash comparison between rear-end and non-rear-end to identify those specific trends of the rear-end crashes. The other was constructed for the comparison between striking vehicles/drivers (at-fault) and struck vehicles/drivers (not-at-fault) to find more complex crash pattern associated with the traffic attributes of driver, vehicle, and environment. The modeling results showed that the rear-end crashes are over-presented in the higher speed limits (45-55 mph); the rear-end crash propensity for daytime is apparently larger than nighttime; and the reduction of braking capacity due to wet and slippery road surface conditions would definitely contribute to rear-end crashes, especially at intersections with higher speed limits. The tree model segmented drivers into four homogeneous age groups: < 21 years, 21-31 years, 32-75 years, and > 75 years. The youngest driver group shows the largest crash propensity; in the 21-31 age group, the male drivers are over-involved in rear-end crashes under adverse weather conditions and the 32-75 years drivers driving large size vehicles have a larger crash propensity compared to those driving passenger vehicles. Combined with the quasi-induced exposure concept, the classification tree method is a proper statistical tool for traffic-safety analysis to investigate crash propensity. Compared to the logistic regression models, tree models have advantages for handling continuous independent variables and easily explaining the complex interaction effect with more than two independent variables. This research recommended that at signalized intersections with higher speed limits, reducing the speed limit to 40 mph efficiently contribute to a lower accident rate. Drivers involved in alcohol use may increase not only rear-end crash risk but also the driver injury severity. Education and enforcement countermeasures should focus on the driver group younger than 21 years. Further studies are suggested to compare crash risk distributions of the driver age for other main crash types to seek corresponding traffic countermeasures.

Evaluation of work zone speed limits : an objective and subjective analysis of work zones in Missouri.

DOT National Transportation Integrated Search

2011-02-01

This study objectively and subjectively examined speed characteristics and driver compliance with the posted speed limit : in Missouri work zones. The objective evaluation collected vehicle speeds from four work zones with different : configurations ...

Variable Speed Limit (VSL) - Best Management Practice

DOT National Transportation Integrated Search

2012-07-01

The Variable Speed Limit (VSL) system on the I-4 corridor in Orlando was implemented by Florida Department of Transportation in 2008, and since its deployment, it was revealed that the majority of traffic exceeds the speed limit by more mph when the ...

Evaluating outcomes of raising speed limits on high speed non-freeways.

DOT National Transportation Integrated Search

2015-04-01

The purpose of this research was to assist in determining the potential impacts of implementing a : proposed 65 mph speed limit on non-freeways in Michigan. Consideration was given to a broad range of : performance measures, including operating speed...

Cost-benefit evaluation of large truck-automobile speed limit differentials on rural interstate highways.

DOT National Transportation Integrated Search

2005-11-01

Speed differentials between large trucks and automobiles on rural interstate highways are due to : both state regulated speed limits and commercial trucking company policies that restrict maximum truck : speeds. The initial portion of this effort inv...

Peer influence on speeding behaviour among male drivers aged 18 and 28.

PubMed

Møller, Mette; Haustein, Sonja

2014-03-01

Despite extensive research, preventive efforts and general improvements in road safety levels, the accident risk of young male drivers remains increased. Based on a standardized survey of a random sample of 2018 male drivers at the age of 18 and 28, this study looked into attitudes and behaviours related to traffic violations of male drivers. More specifically, the role of peer influence on speeding was examined in both age groups. In regression analyses it could be shown that the descriptive subjective norm, i.e., the perception of friends' speeding, was the most important predictor of speeding in both age groups. Other significant factors were: negative attitude towards speed limits, injunctive subjective norm, and the perceived risk of having an accident when speeding. In the older age group it was more common to drive faster than allowed and their speeding was largely in line with the perceived level of their friends' speeding. In the younger age group a higher discrepancy between own and friends' speeding was found indicating that young male drivers are socialized into increased speeding behaviour based on peer pressure. By contrast for the 28-year-olds peer pressure mainly seems to maintain or justify individual speeding behaviour. It is suggested that preventive measures should take these different influences of peer pressure into account by using a peer-based approach for the 18-year-olds and a more individual approach for the 28-year-olds. Copyright © 2013 Elsevier Ltd. All rights reserved.

Work zone variable speed limit systems: Effectiveness and system design issues.

DOT National Transportation Integrated Search

2010-03-01

Variable speed limit (VSL) systems have been used in a number of countries, particularly in Europe, as a method to improve flow and increase safety. VSLs use detectors to collect data on current traffic and/or weather conditions. Posted speed limits ...

Work zone variable speed limit systems : effectiveness and system design issues.

DOT National Transportation Integrated Search

2010-03-01

Variable speed limit (VSL) systems have been used in a number of countries, particularly in Europe, as a method to improve flow and increase safety. VSLs use detectors to collect data on current traffic and/or weather conditions. Posted speed limits ...

Field test of the impact of setting and enforcing rational speed limits : final report for Gulfport, Mississippi--demonstration community

DOT National Transportation Integrated Search

2007-10-01

To address concerns regarding the need to restore credibility to speed limits, the National Highway Traffic Safety Administration (NHTSA) and the Federal Highway Administration (FHWA) jointly undertook tests of rational speed limits, which have...

Impact of the 65 mph speed limit on Virginia's rural interstate highways, 1989-1992.

DOT National Transportation Integrated Search

1994-01-01

In April of 1987, Congress passed the Surface Transportation and Uniform Relocation Assistance Act (STURAA), which permitted states to raise their maximum speed limit on rural interstate highways to 65 mph. Virginia's 65 mph speed limit went into eff...

Field Validation of the Stability Limit of a Multi MW Turbine

NASA Astrophysics Data System (ADS)

Kallesøe, Bjarne S.; Kragh, Knud A.

2016-09-01

Long slender blades of modern multi-megawatt turbines exhibit a flutter like instability at rotor speeds above a critical rotor speed. Knowing the critical rotor speed is crucial to a safe turbine design. The flutter like instability can only be estimated using geometrically non-linear aeroelastic codes. In this study, the estimated rotor speed stability limit of a 7 MW state of the art wind turbine is validated experimentally. The stability limit is estimated using Siemens Wind Powers in-house aeroelastic code, and the results show that the predicted stability limit is within 5% of the experimentally observed limit.

40 CFR 1037.640 - Variable vehicle speed limiters.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 34 2012-07-01 2012-07-01 false Variable vehicle speed limiters. 1037... POLLUTION CONTROLS CONTROL OF EMISSIONS FROM NEW HEAVY-DUTY MOTOR VEHICLES Special Compliance Provisions § 1037.640 Variable vehicle speed limiters. This section specifies provisions that apply for vehicle...

40 CFR 1037.640 - Variable vehicle speed limiters.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 34 2013-07-01 2013-07-01 false Variable vehicle speed limiters. 1037... POLLUTION CONTROLS CONTROL OF EMISSIONS FROM NEW HEAVY-DUTY MOTOR VEHICLES Special Compliance Provisions § 1037.640 Variable vehicle speed limiters. This section specifies provisions that apply for vehicle...

Visualization of hump formation in high-speed gas metal arc welding

NASA Astrophysics Data System (ADS)

Wu, C. S.; Zhong, L. M.; Gao, J. Q.

2009-11-01

The hump bead is a typical weld defect observed in high-speed welding. Its occurrence limits the improvement of welding productivity. Visualization of hump formation during high-speed gas metal arc welding (GMAW) is helpful in the better understanding of the humping phenomena so that effective measures can be taken to suppress or decrease the tendency of hump formation and achieve higher productivity welding. In this study, an experimental system was developed to implement vision-based observation of the weld pool behavior during high-speed GMAW. Considering the weld pool characteristics in high-speed welding, a narrow band-pass and neutral density filter was equipped for the CCD camera, the suitable exposure time was selected and side view orientation of the CCD camera was employed. The events that took place at the rear portion of the weld pools were imaged during the welding processes with and without hump bead formation, respectively. It was found that the variation of the weld pool surface height and the solid-liquid interface at the pool trailing with time shows some useful information to judge whether the humping phenomenon occurs or not.

Cost-benefit analysis of the 55-mph speed limit

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

Forester, T.H.; McNown, R.F.; Singell, L.D.

1984-01-01

This article presents the results of an empirical study which estimates the number of reduced fatalities as a result of the imposed 55-mph speed limit. Time series data for the US from 1952 to 1979 is employed in a regression model capturing the relation between fatalities, average speed, variability of speed, and the speed limit. Also discussed are the alternative approaches to valuing human life and the value of time. Provided is a series of benefit-cost ratios based on alternative measures of the benefits and costs from life saving. The paper concludes that the 55-mph speed limit is not costmore » efficient unless additional time on the highway is valued significantly below levels estimated in the best reasearch on the value of time. 12 references, 1 table.« less

Lorre cluster: an outcome of recent asteroid collision

NASA Astrophysics Data System (ADS)

Novakovic, B.; Dell'Oro, A.; Cellino, A.; Knezevic, Z.

2012-09-01

Here we show an example of a young asteroid cluster located in a dynamically stable region, which was produced by partial disruption of a primitive body about 30 km in size. According to our estimation it is only 1.9±0.3 Myr old, thus its post-impact evolution is very limited. The parent body had a large orbital inclination, and was subject to collisions with typical impact speeds higher by a factor of 2 than in the most common situations encountered in the main belt. For the first time we have at disposal the observable outcome of a very recent event to study high-speed collisions involving primitive asteroids.

Modelling and control of solid oxide fuel cell generation system in microgrid

NASA Astrophysics Data System (ADS)

Zhou, Niancheng; Li, Chunyan; Sun, Fangqing; Wang, Qianggang

2017-11-01

Compared with other kinds of fuel cells, solid oxide fuel cell (SOFC) has been widely used in microgrids because of its higher efficiency and longer operation life. The weakness of SOFC lies in its slow response speed when grid disturbance occurs. This paper presents a control strategy that can promote the response speed and limit the fault current impulse for SOFC systems integrated into microgrids. First, the hysteretic control of the bidirectional DC-DC converter, which joins the SOFC and DC bus together, is explored. In addition, an improved droop control with limited current protection is applied in the DC-AC inverter, and the active synchronization control is applied to ensure a smooth transition of the microgrid between the grid-connected mode and the islanded mode. To validate the effectiveness of this control strategy, the control model was built and simulated in PSCAD/EMTDC.

Diffusiophoresis of charged colloidal particles in the limit of very high salinity.

PubMed

Prieve, Dennis C; Malone, Stephanie M; Khair, Aditya S; Stout, Robert F; Kanj, Mazen Y

2018-06-13

Diffusiophoresis is the migration of a colloidal particle through a viscous fluid, caused by a gradient in concentration of some molecular solute; a long-range physical interaction between the particle and solute molecules is required. In the case of a charged particle and an ionic solute (e.g., table salt, NaCl), previous studies have predicted and experimentally verified the speed for very low salt concentrations at which the salt solution behaves ideally. The current study presents a study of diffusiophoresis at much higher salt concentrations (approaching the solubility limit). At such large salt concentrations, electrostatic interactions are almost completely screened, thus eliminating the long-range interaction required for diffusiophoresis; moreover, the high volume fraction occupied by ions makes the solution highly nonideal. Diffusiophoretic speeds were found to be measurable, albeit much smaller than for the same gradient at low salt concentrations.

50 CFR 38.13 - Speed limits.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 50 Wildlife and Fisheries 8 2011-10-01 2011-10-01 false Speed limits. 38.13 Section 38.13 Wildlife and Fisheries UNITED STATES FISH AND WILDLIFE SERVICE, DEPARTMENT OF THE INTERIOR (CONTINUED) THE NATIONAL WILDLIFE REFUGE SYSTEM MIDWAY ATOLL NATIONAL WILDLIFE REFUGE Prohibitions § 38.13 Speed limits. No...

50 CFR 38.13 - Speed limits.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 50 Wildlife and Fisheries 9 2013-10-01 2013-10-01 false Speed limits. 38.13 Section 38.13 Wildlife and Fisheries UNITED STATES FISH AND WILDLIFE SERVICE, DEPARTMENT OF THE INTERIOR (CONTINUED) THE NATIONAL WILDLIFE REFUGE SYSTEM MIDWAY ATOLL NATIONAL WILDLIFE REFUGE Prohibitions § 38.13 Speed limits. No...

50 CFR 38.13 - Speed limits.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 50 Wildlife and Fisheries 9 2014-10-01 2014-10-01 false Speed limits. 38.13 Section 38.13 Wildlife and Fisheries UNITED STATES FISH AND WILDLIFE SERVICE, DEPARTMENT OF THE INTERIOR (CONTINUED) THE NATIONAL WILDLIFE REFUGE SYSTEM MIDWAY ATOLL NATIONAL WILDLIFE REFUGE Prohibitions § 38.13 Speed limits. No...

50 CFR 38.13 - Speed limits.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 50 Wildlife and Fisheries 9 2012-10-01 2012-10-01 false Speed limits. 38.13 Section 38.13 Wildlife and Fisheries UNITED STATES FISH AND WILDLIFE SERVICE, DEPARTMENT OF THE INTERIOR (CONTINUED) THE NATIONAL WILDLIFE REFUGE SYSTEM MIDWAY ATOLL NATIONAL WILDLIFE REFUGE Prohibitions § 38.13 Speed limits. No...

Obesity history as a predictor of walking limitation at old age.

PubMed

Stenholm, Sari; Rantanen, Taina; Alanen, Erkki; Reunanen, Antti; Sainio, Päivi; Koskinen, Seppo

2007-04-01

To study whether walking limitation at old age is determined by obesity history. In a retrospective longitudinal study based on a representative sample of the Finnish population of 55 years and older (2055 women and 1337 men), maximal walking speed, body mass, and body height were measured in a health examination. Walking limitation was defined as walking speed<1.2 m/s or difficulty in walking 0.5 km. Recalled height at 20 years of age and recalled weight at 20, 30, 40, and 50 years of age were recorded. Subjects who had been obese at the age of 30, 40, or 50 years had almost a 4-fold higher risk of walking limitation compared to non-obese. Obesity duration increased the age- and gender-adjusted risk of walking limitation among those who had been obese since the age of 50 (odds ratio, 4.33; 95% confidence interval, 2.59 to 7.23, n=114), among the obese since the age of 40 [6.01 (2.55 to 14.14), n=39], and among the obese since the age of 30 [8.97 (3.06 to 26.29), n=14]. The risk remained elevated even among those who had previously been obese but lost weight during their midlife or late adulthood [3.15 (1.63 to 6.11), n=71]. Early onset of obesity and obesity duration increased the risk of walking limitation, and the effect was only partially mediated through current BMI and higher risk of obesity-related diseases. Preventing excess weight gain throughout one's life course is an important goal in order to promote good health and functioning in older age.

Sparse distributed memory: understanding the speed and robustness of expert memory

PubMed Central

Brogliato, Marcelo S.; Chada, Daniel M.; Linhares, Alexandre

2014-01-01

How can experts, sometimes in exacting detail, almost immediately and very precisely recall memory items from a vast repertoire? The problem in which we will be interested concerns models of theoretical neuroscience that could explain the speed and robustness of an expert's recollection. The approach is based on Sparse Distributed Memory, which has been shown to be plausible, both in a neuroscientific and in a psychological manner, in a number of ways. A crucial characteristic concerns the limits of human recollection, the “tip-of-tongue” memory event—which is found at a non-linearity in the model. We expand the theoretical framework, deriving an optimization formula to solve this non-linearity. Numerical results demonstrate how the higher frequency of rehearsal, through work or study, immediately increases the robustness and speed associated with expert memory. PMID:24808842

A critical assessment of the Burning Index in Los Angeles County, California

USGS Publications Warehouse

Schoenberg, F.P.; Chang, H.-C.; Keeley, J.E.; Pompa, J.; Woods, J.; Xu, H.

2007-01-01

The Burning Index (BI) is commonly used as a predictor of wildfire activity. An examination of data on the BI and wildfires in Los Angeles County, California, from January 1976 to December 2000 reveals that although the BI is positively associated with wildfire occurrence, its predictive value is quite limited. Wind speed alone has a higher correlation with burn area than BI, for instance, and a simple alternative point process model using wind speed, relative humidity, precipitation and temperature well outperforms the BI in terms of predictive power. The BI is generally far too high in winter and too low in fall, and may exaggerate the impact of individual variables such as wind speed or temperature during times when other variables, such as precipitation or relative humidity, render the environment ill suited for wildfires. ?? IAWF 2007.

Higher speed freight truck : vehicle dynamics analysis.

DOT National Transportation Integrated Search

2015-08-01

Previously, Sharma & Associates, Inc. (SA) developed a higher speed freight truck design under sponsorship of the Federal : Railroad Administration. Under the current contract, SA was tasked with developing performance requirements for higher speed :...

Evaluation of 70 mph speed limit in Kentucky.

DOT National Transportation Integrated Search

2008-05-01

The objective of this study was to document the change in operating speeds of cars and trucks on rural interstates and parkways as a result of the change in speed limit from 65 mph to 70 mph. The 85th percentile speed increased 1.3 mph for cars (74.6...

36 CFR § 1004.21 - Speed limits.

Code of Federal Regulations, 2013 CFR

2013-07-01

... determine the speed of a vehicle on a Presidio Trust road. Signs indicating that vehicle speed is determined... hour: upon sections of Presidio Trust road under repair or construction. (3) 45 miles per hour: upon all other Presidio Trust roads. (b) The Board may designate a different speed limit upon any Presidio...

Hybrid Welding of 45 mm High Strength Steel Sections

NASA Astrophysics Data System (ADS)

Bunaziv, Ivan; Frostevarg, Jan; Akselsen, Odd M.; Kaplan, Alexander F.

Thick section welding has significant importance for oil and gas industry in low temperature regions. Arc welding is usually employed providing suitable quality joints with acceptable toughness at low temperatures with very limited productivity compared to modern high power laser systems. Laser-arc hybrid welding (LAHW) can enhance the productivity by several times due to higher penetration depth from laser beam and combined advantages of both heat sources. LAHW was applied to join 45 mm high strength steel with double-sided technique and application of metal cored wire. The process was captured by high speed camera, allowing process observation in order to identify the relation of the process stability on weld imperfections and efficiency. Among the results, it was found that both arc power and presence of a gap increased penetration depth, and that higher welding speeds cause unstable processing and limits penetration depth. Over a wide range of heat inputs, the welds where found to consist of large amounts of fine-grained acicular ferrite in the upper 60-75% part of welds. At the root filler wire mixing was less and cooling faster, and thus found to have bainitic transformation. Toughness of deposited welds provided acceptable toughness at -50 °C with some scattering.

Wind Resource Assessment in Complex Terrain with a High-Resolution Numerical Weather Prediction Model

NASA Astrophysics Data System (ADS)

Gruber, Karin; Serafin, Stefano; Grubišić, Vanda; Dorninger, Manfred; Zauner, Rudolf; Fink, Martin

2014-05-01

A crucial step in planning new wind farms is the estimation of the amount of wind energy that can be harvested in possible target sites. Wind resource assessment traditionally entails deployment of masts equipped for wind speed measurements at several heights for a reasonably long period of time. Simplified linear models of atmospheric flow are then used for a spatial extrapolation of point measurements to a wide area. While linear models have been successfully applied in the wind resource assessment in plains and offshore, their reliability in complex terrain is generally poor. This represents a major limitation to wind resource assessment in Austria, where high-altitude locations are being considered for new plant sites, given the higher frequency of sustained winds at such sites. The limitations of linear models stem from two key assumptions in their formulation, the neutral stratification and attached boundary-layer flow, both of which often break down in complex terrain. Consequently, an accurate modeling of near-surface flow over mountains requires the adoption of a NWP model with high horizontal and vertical resolution. This study explores the wind potential of a site in Styria in the North-Eastern Alps. The WRF model is used for simulations with a maximum horizontal resolution of 800 m. Three nested computational domains are defined, with the innermost one encompassing a stretch of the relatively broad Enns Valley, flanked by the main crest of the Alps in the south and the Nördliche Kalkalpen of similar height in the north. In addition to the simulation results, we use data from fourteen 10-m wind measurement sites (of which 7 are located within valleys and 5 near mountain tops) and from 2 masts with anemometers at several heights (at hillside locations) in an area of 1600 km2 around the target site. The potential for wind energy production is assessed using the mean wind speed and turbulence intensity at hub height. The capacity factor is also evaluated, considering the frequency of wind speed between cut-in and cut-out speed and of winds with a low vertical velocity component only. Wind turbines do not turn on at wind speeds below cut-in speed. Wind turbines are taken off from the generator in the case of wind speeds higher than cut-out speed and inclination angles of the wind vector greater than 8o. All of these parameters were computed at each model grid point in the innermost domain in order to map their spatial variability. The results show that in complex terrain the annual mean wind speed at hub height is not sufficient to predict the capacity factor of a turbine; vertical wind speed and the frequency of horizontal wind speed out of the range of cut-in and cut-out speed contribute substantially to a reduction of the energy harvest and locally high turbulence may considerably raise the building costs.

Investigations of Section Speed on Rural Roads in Podlaskie Voivodeship

NASA Astrophysics Data System (ADS)

Ziolkowski, Robert

2017-10-01

Excessive speed is one of the most important factors considered in road safety and not only affects the severity of a crash but is also related to the risk of being involved in a crash. In Poland the problem of speeding drivers is widely common. Properly recognized and defined drivers behaviour is the base for any effective activities taken towards road safety improvements. Effective enforcement of speed limits especially on rural road plays an important role but conducted speed investigations basically focus on spot speed omitting travel speed on longer sections of roads which can better reflect driver’s behaviour. Possible solutions for rural roads are limited to administrative means of speed limitations, installations of speed cameras and police enforcement. However due to their limited proved effectiveness new solutions are still being sought. High expectations are associated with the sectional speed system that has recently been introduced in Poland and covered a number of national road sections. The aim of this paper is to investigate section speed on chosen regional and district roads located in Podlaskie Voivodeship. Test sections included 19 road segments varied in terms of functional and geometric characteristics. Speed measurements on regional and district roads were performed with the use of a set of two ANPR (Automatic Number Plate Recognition) cameras. Conducted research allowed to compare driver’s behaviour in terms of travel speed depending on roads’ functional classification as well as to evaluate the influence of chosen geometric parameters on average section speed.

Assessment of potential aerodynamic effects on personnel and equipment in proximity to high-speed train operations : safety of high-speed ground transportation systems

DOT National Transportation Integrated Search

1999-12-01

Amtrak is planning to provide high-speed passenger train service at speeds significantly higher than their current top speed of 125 mph, and with these higher speeds, there are concerns with safety from the aerodynamic effects created by a passing tr...

Cruise noise of the SR-2 propeller model in a wind tunnel

NASA Technical Reports Server (NTRS)

Dittmar, James H.

1989-01-01

Noise data on the SR-2 model propeller were taken in the NASA Lewis Research Center 8- by 6-Foot Wind Tunnel. The maximum blade passing tone rises with increasing helical tip Mach number to a peak level at a helical tip Mach number of about 1.05; then it remains the same or decreases at higher helical tip Mach numbers. This behavior, which has been observed with other propeller models, points to the possibility of using higher propeller tip speeds to limit airplane cabin noise while maintaining high flight speed and efficiency. Noise comparisons of the straight-blade SR-2 propeller and the swept-blade SR-7A propeller showed that the tailored sweep of the SR-7A appears to be the cause of both lower peak noise levels and a slower noise increase with increasing helical tip Mach number.

Bio-logging of physiological parameters in higher marine vertebrates

NASA Astrophysics Data System (ADS)

Ponganis, Paul J.

2007-02-01

Bio-logging of physiological parameters in higher marine vertebrates had its origins in the field of bio-telemetry in the 1960s and 1970s. The development of microprocessor technology allowed its first application to bio-logging investigations of Weddell seal diving physiology in the early 1980s. Since that time, with the use of increased memory capacity, new sensor technology, and novel data processing techniques, investigators have examined heart rate, temperature, swim speed, stroke frequency, stomach function (gastric pH and motility), heat flux, muscle oxygenation, respiratory rate, diving air volume, and oxygen partial pressure (P) during diving. Swim speed, heart rate, and body temperature have been the most commonly studied parameters. Bio-logging investigation of pressure effects has only been conducted with the use of blood samplers and nitrogen analyses on animals diving at isolated dive holes. The advantages/disadvantages and limitations of recording techniques, probe placement, calibration techniques, and study conditions are reviewed.

Vibration compensation for high speed scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Croft, D.; Devasia, S.

1999-12-01

Low scanning speed is a fundamental limitation of scanning tunneling microscopes (STMs), making real time imaging of surface processes and nanofabrication impractical. The effective scanning bandwidth is currently limited by the smallest resonant vibrational frequency of the piezobased positioning system (i.e., scanner) used in the STM. Due to this limitation, the acquired images are distorted during high speed operations. In practice, the achievable scan rates are much less than 1/10th of the resonant vibrational frequency of the STM scanner. To alleviate the scanning speed limitation, this article describes an inversion-based approach that compensates for the structural vibrations in the scanner and thus, allows STM imaging at high scanning speeds (relative to the smallest resonant vibrational frequency). Experimental results are presented to show the increase in scanning speeds achievable by applying the vibration compensation methods.

The credibility of speed limits on 80 km/h rural roads: The effects of road and person(ality) characteristics.

PubMed

Goldenbeld, Charles; van Schagen, Ingrid

2007-11-01

The present study aimed to operationalise the concept of credible speed limits and to make a first step to elaborate it in such a way that road authorities can put the concept into practice. The study focused on the credibility of an 80 km/h limit for different rural roads and assessed the effects of characteristics of the road and its environment as well as the effects of person and personality characteristics. Almost 600 Dutch car drivers were asked to judge 27 photographs of (different) rural roads with a posted speed limit of 80 km/h. To determine the degree of credibility, for each road scene the subjects filled in the preferred speed and the speed limit they considered to be safe. The results show large differences in both preferred speed and the safe speed limit between the road scenes, both below and above the limit of 80 km/h. These differences were related to a number of characteristics of the road and the road environment, such as the presence or absence of a curve and characteristics concerning the field of view (sight distance, clarity of situation). There were also large differences between subjects and these were related to age, the degree of sensation seeking, the number of speeding tickets in the last 3 years and the part of the country they lived in. Subjects were influenced by more or less the same road features.

32 CFR 935.132 - Speed limits.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 32 National Defense 6 2014-07-01 2014-07-01 false Speed limits. 935.132 Section 935.132 National... WAKE ISLAND CODE Motor Vehicle Code § 935.132 Speed limits. Each person operating a motor vehicle on... day, road and weather conditions, the kind of motor vehicle, and the proximity to persons or buildings...

32 CFR 935.132 - Speed limits.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 32 National Defense 6 2013-07-01 2013-07-01 false Speed limits. 935.132 Section 935.132 National... WAKE ISLAND CODE Motor Vehicle Code § 935.132 Speed limits. Each person operating a motor vehicle on... day, road and weather conditions, the kind of motor vehicle, and the proximity to persons or buildings...

32 CFR 935.132 - Speed limits.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 32 National Defense 6 2012-07-01 2012-07-01 false Speed limits. 935.132 Section 935.132 National... WAKE ISLAND CODE Motor Vehicle Code § 935.132 Speed limits. Each person operating a motor vehicle on... day, road and weather conditions, the kind of motor vehicle, and the proximity to persons or buildings...

32 CFR 935.132 - Speed limits.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 32 National Defense 6 2010-07-01 2010-07-01 false Speed limits. 935.132 Section 935.132 National... WAKE ISLAND CODE Motor Vehicle Code § 935.132 Speed limits. Each person operating a motor vehicle on Wake Island shall operate it at a speed— (a) That is reasonable, safe, and proper, considering time of...

32 CFR 935.132 - Speed limits.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 32 National Defense 6 2011-07-01 2011-07-01 false Speed limits. 935.132 Section 935.132 National... WAKE ISLAND CODE Motor Vehicle Code § 935.132 Speed limits. Each person operating a motor vehicle on Wake Island shall operate it at a speed— (a) That is reasonable, safe, and proper, considering time of...

Tightening Quantum Speed Limits for Almost All States.

PubMed

Campaioli, Francesco; Pollock, Felix A; Binder, Felix C; Modi, Kavan

2018-02-09

Conventional quantum speed limits perform poorly for mixed quantum states: They are generally not tight and often significantly underestimate the fastest possible evolution speed. To remedy this, for unitary driving, we derive two quantum speed limits that outperform the traditional bounds for almost all quantum states. Moreover, our bounds are significantly simpler to compute as well as experimentally more accessible. Our bounds have a clear geometric interpretation; they arise from the evaluation of the angle between generalized Bloch vectors.

Timing performance of a self-cancelling turn-signal mechanism in motorcycles based on the ATMega328P microcontroller

NASA Astrophysics Data System (ADS)

Nurbuwat, Adzin Kondo; Eryandi, Kholid Yusuf; Estriyanto, Yuyun; Widiastuti, Indah; Pambudi, Nugroho Agung

2018-02-01

The objective of this study is to measure the time performance of a self-cancelling turn signal mechanism based on the In this study the performance of self-cancelling turn signal based on ATMega328P microcontroller is measured at low speed and high speed treatment on motorcycles commonly used in Indonesia. Time performance measurements were made by comparing the self-cancelling turn signal based on ATMega328P microcontroller with standard motor turn time. Measurements of time at low speed treatment were performed at a speed range of 15 km / h, 20 km / h, 25 km / h on the U-turn test trajectory. The angle of the turning angle of the potentiometer is determined at 3°. The limit of steering wheel turning angle at the potentiometer is set at 3°. For high-speed treatment is 30 km / h, 40 km / h, 50km / h, and 60 km / h, on the L-turn test track with a tilt angle (roll angle) read by the L3G4200D gyroscope sensor. Each speed test is repeated 3 replications. Standard time is a reference for self-cancelling turn signal performance. The standard time obtained is 15.68 s, 11.96 s, 9.34 s at low speed and 4.63 s, 4.06 s, 3.61 s, 3.13 s at high speed. The time test of self-cancelling turn signal shows 16.10 s, 12.42 s, 10.24 s at the low speed and 5.18, 4.51, 3.73, 3.21 at the high speed. At a speed of 15 km / h occurs the instability of motion turns motorcycle so that testing is more difficult. Small time deviations indicate the tool works well. The largest time deviation value is 0.9 seconds at low speed and 0.55 seconds at high speed. The conclusion at low velocity of the highest deviation value occurred at the speed of 25 km / h test due to the movement of slope with inclination has started to happen which resulted in slow reading of steering movement. At higher speeds the time slows down due to rapid sensor readings on the tilt when turning fast at ever higher speeds. The timing performance of self-cancelling turn signal decreases as the motorcycle turning characteristics move from the turn using the steering angle to using a tilt angle based on speed, or vice versa.

Young drivers' perception of adult and child pedestrians in potential street-crossing situations.

PubMed

Ābele, Līva; Haustein, Sonja; Møller, Mette

2018-04-03

Despite overall improvements in road traffic safety, pedestrian accidents continue to be a serious public health problem. Due to lack of experience, limited cognitive and motoric skills, and smaller size, children have a higher injury risk as pedestrians than adults. To what extent drivers adjust their driving behaviour to children's higher vulnerability is largely unknown. To determine whether young male drivers' behaviour and scanning pattern differs when approaching a child and an adult pedestrian in a potential street-crossing situation, sixty-five young (18-24) male drivers' speed, lateral position and eye movements were recorded in a driving simulator. Results showed that fewer drivers responded by slowing down and that drivers had a higher driving speed when approaching a child pedestrian, although the time of the first fixation on both types of pedestrians was the same. However, drivers drove farther away from a child than an adult pedestrian. Additionally, fewer drivers who did not slow down fixated on the speedometer while approaching the child pedestrian. The results show that young drivers behave differently when approaching a child and an adult pedestrian, though not in a way that appropriately accounts for the limitations of a child pedestrian. A better understanding of how drivers respond to different types of pedestrians and why could contribute to the development of pedestrian detection and emergency braking systems. Copyright © 2018 Elsevier Ltd. All rights reserved.

Perils of using speed zone data to assess real-world compliance to speed limits.

PubMed

Chevalier, Anna; Clarke, Elizabeth; Chevalier, Aran John; Brown, Julie; Coxon, Kristy; Ivers, Rebecca; Keay, Lisa

2017-11-17

Real-world driving studies, including those involving speeding alert devices and autonomous vehicles, can gauge an individual vehicle's speeding behavior by comparing measured speed with mapped speed zone data. However, there are complexities with developing and maintaining a database of mapped speed zones over a large geographic area that may lead to inaccuracies within the data set. When this approach is applied to large-scale real-world driving data or speeding alert device data to determine speeding behavior, these inaccuracies may result in invalid identification of speeding. We investigated speeding events based on service provider speed zone data. We compared service provider speed zone data (Speed Alert by Smart Car Technologies Pty Ltd., Ultimo, NSW, Australia) against a second set of speed zone data (Google Maps Application Programming Interface [API] mapped speed zones). We found a systematic error in the zones where speed limits of 50-60 km/h, typical of local roads, were allocated to high-speed motorways, which produced false speed limits in the speed zone database. The result was detection of false-positive high-range speeding. Through comparison of the service provider speed zone data against a second set of speed zone data, we were able to identify and eliminate data most affected by this systematic error, thereby establishing a data set of speeding events with a high level of sensitivity (a true positive rate of 92% or 6,412/6,960). Mapped speed zones can be a source of error in real-world driving when examining vehicle speed. We explored the types of inaccuracies found within speed zone data and recommend that a second set of speed zone data be utilized when investigating speeding behavior or developing mapped speed zone data to minimize inaccuracy in estimates of speeding.

High diving metabolic rate indicated by high-speed transit to depth in negatively buoyant long-finned pilot whales.

PubMed

Aoki, Kagari; Sato, Katsufumi; Isojunno, Saana; Narazaki, Tomoko; Miller, Patrick J O

2017-10-15

To maximize foraging duration at depth, diving mammals are expected to use the lowest cost optimal speed during descent and ascent transit and to minimize the cost of transport by achieving neutral buoyancy. Here, we outfitted 18 deep-diving long-finned pilot whales with multi-sensor data loggers and found indications that their diving strategy is associated with higher costs than those of other deep-diving toothed whales . Theoretical models predict that optimal speed is proportional to (basal metabolic rate/drag) 1/3 and therefore to body mass 0.05 The transit speed of tagged animals (2.7±0.3 m s -1 ) was substantially higher than the optimal speed predicted from body mass (1.4-1.7 m s -1 ). According to the theoretical models, this choice of high transit speed, given a similar drag coefficient (median, 0.0035) to that in other cetaceans, indicated greater basal metabolic costs during diving than for other cetaceans. This could explain the comparatively short duration (8.9±1.5 min) of their deep dives (maximum depth, 444±85 m). Hydrodynamic gliding models indicated negative buoyancy of tissue body density (1038.8±1.6 kg m -3 , ±95% credible interval, CI) and similar diving gas volume (34.6±0.6 ml kg -1 , ±95% CI) to those in other deep-diving toothed whales. High diving metabolic rate and costly negative buoyancy imply a 'spend more, gain more' strategy of long-finned pilot whales, differing from that in other deep-diving toothed whales, which limits the costs of locomotion during foraging. We also found that net buoyancy affected the optimal speed: high transit speeds gradually decreased during ascent as the whales approached neutral buoyancy owing to gas expansion. © 2017. Published by The Company of Biologists Ltd.

Reward Pays the Cost of Noise Reduction in Motor and Cognitive Control.

PubMed

Manohar, Sanjay G; Chong, Trevor T-J; Apps, Matthew A J; Batla, Amit; Stamelou, Maria; Jarman, Paul R; Bhatia, Kailash P; Husain, Masud

2015-06-29

Speed-accuracy trade-off is an intensively studied law governing almost all behavioral tasks across species. Here we show that motivation by reward breaks this law, by simultaneously invigorating movement and improving response precision. We devised a model to explain this paradoxical effect of reward by considering a new factor: the cost of control. Exerting control to improve response precision might itself come at a cost--a cost to attenuate a proportion of intrinsic neural noise. Applying a noise-reduction cost to optimal motor control predicted that reward can increase both velocity and accuracy. Similarly, application to decision-making predicted that reward reduces reaction times and errors in cognitive control. We used a novel saccadic distraction task to quantify the speed and accuracy of both movements and decisions under varying reward. Both faster speeds and smaller errors were observed with higher incentives, with the results best fitted by a model including a precision cost. Recent theories consider dopamine to be a key neuromodulator in mediating motivational effects of reward. We therefore examined how Parkinson's disease (PD), a condition associated with dopamine depletion, alters the effects of reward. Individuals with PD showed reduced reward sensitivity in their speed and accuracy, consistent in our model with higher noise-control costs. Including a cost of control over noise explains how reward may allow apparent performance limits to be surpassed. On this view, the pattern of reduced reward sensitivity in PD patients can specifically be accounted for by a higher cost for controlling noise. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

The effects of roadway characteristics on farm equipment crashes: A GIS approach

NASA Astrophysics Data System (ADS)

Greenan, Mitchell Joseph

Tractors and other self-propelled farm equipment, such as combines, sprayers, and towed grain carts, are often used on public roadways as the primary means for traveling from homestead to homestead or from homestead to a distributer. Increased roadway exposure has led to a growing concern for crashes involving farm equipment on the public roadway. A handful of studies exist examining public roadway crashes involving farm equipment using crash data, but none thus far have evaluated road segment data to identify road-specific risk factors. The objective of this study is to identify if roadway characteristics (traffic density, speed limit, road type, surface type, road width, and shoulder width) affect the risk of a crash involving farm equipment on Iowa public roadways. A retrospective cohort study of Iowa roads was conducted to identify the types of roads that are at an increased risk of having a farm-equipment crash on them. Crash data from the Iowa Department of Transportation (to identify crashes) were spatial linked to Iowa roadway data using Geographic Information Systems (GIS). Logistic regression was used to calculate ORs and 95% CL. Out of 319,705 road segments in Iowa, 0.4% segments (n=1,337) had a farm equipment crash from 2005-2011. The odds of having a farm equipment crash were significantly higher for road segments with increased traffic density and speed limit. Roads with an average daily traffic volume of at least 1,251 vehicles were at a 5.53 times greater odds of having a crash than roads with a daily traffic volume between 0-30 vehicles. (CI: 3.90-7.83). Roads with a posted speed limit between 50mph and 60mph were at a 4.88 times greater odds of having a crash than roads with a posted speed limit of 30mph or less. (CI: 3.85-6.20). Specific roadway characteristics such as roadway and shoulder width were also associated with the risk of a crash. For every 5 foot increase in road width, the odds for a crash decreased by 6 percent (CI: 0.89-0.99) and for every 5 foot increase in shoulder width, the odds of a crash decreased by 8 percent. (CI: 0.86-0.98). Although not statically significant, unpaved roads increased the odds of a crash by 17 percent. (CI: 0.91-1.50) Lastly, it was found that Farm to Market routes increased the odds of a crash by two fold compared to local roads (which make up roughly 67 percent of Iowa public roads). (CI: 1.72-2.43) When the same model was stratified by rurality (urban/rural), it was found that high traffic density leads to a higher risk of a crash in rural areas. Iowa routes and Farm to Market routes had a greater odds of a crash in urban than rural areas, and road and shoulder width were more protective in rural than urban areas. When only using roads with a crash involving an injury versus all other roads as the outcome, Iowa routes and roads with increased speed limits had higher odds for an injury-involved crash, while increased road width were more protective against crashes involving injuries. Findings from the study suggest that several roadway characteristics were associated with farm-equipment crashes. Through administrative and engineering controls, the six static explanatory variables used in this study may be modified to decrease the risk of a farm equipment crash. Speed limit can be modified through administrative controls while traffic density, road and shoulder width, road type, and surface type can be modified through engineering controls. Results from this study provide information that will aid policy-makers in developing safer roads for farm equipment.

A test of local Lorentz invariance with Compton scattering asymmetry

DOE PAGES

Mohanmurthy, Prajwal; Narayan, Amrendra; Dutta, Dipangkar

2016-12-14

Here, we report on a measurement of the constancy and anisotropy of the speed of light relative to the electrons in photon-electron scattering. We also used the Compton scattering asymmetry measured by the new Compton polarimeter in Hall~C at Jefferson Lab to test for deviations from unity of the vacuum refractive index (more » $n$). For photon energies in the range of 9 - 46 MeV, we obtain a new limit of $$1-n < 1.4 \\times 10^{-8}$$. In addition, the absence of sidereal variation over the six month period of the measurement constrains any anisotropies in the speed of light. These constitute the first study of Lorentz invariance using Compton asymmetry. Within the minimal standard model extension framework, our result yield limits on the photon and electron coefficients $$\\tilde{\\kappa}_{0^+}^{YZ}, c_{TX}, \\tilde{\\kappa}_{0^+}^{ZX}$$, and $$c_{TY}$$. Though, these limits are several orders of magnitude larger than the current best limits, they demonstrate the feasibility of using Compton asymmetry for tests of Lorentz invariance. For future parity violating electron scattering experiments at Jefferson Lab we will use higher energy electrons enabling better constraints.« less

78 FR 19981 - Special Conditions: Embraer S.A., Model EMB-550 Airplanes; Flight Envelope Protection: High Speed...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-03

...; Flight Envelope Protection: High Speed Limiting AGENCY: Federal Aviation Administration (FAA), DOT... protection: high speed limiting. As published, the document contained an error in that the Special Conditions...

Metabolic Rate and Ground Reaction Force During Motorized and Non-Motorized Treadmill Exercise

NASA Technical Reports Server (NTRS)

Everett, Meghan E.; Loehr, James A.; DeWitt, John K.; Laughlin, Mitzi; Lee, Stuart M. C.

2010-01-01

PURPOSE: To measure vertical ground reaction force (vGRF) and oxygen consumption (VO2) at several velocities during exercise using a ground-based version of the ISS treadmill in the M and NM modes. METHODS: Subjects (n = 20) walked or ran at 0.89, 1.34, 1.79, 2.24, 2.68, and 3.12 m/s while VO2 and vGRF data were collected. VO2 was measured using open-circuit spirometry (TrueOne 2400, Parvo-Medics). Data were averaged over the last 2 min of each 5-min stage. vGRF was measured in separate 15-s bouts at 125 Hz using custom-fitted pressure-sensing insoles (F-Scan Sport Sensors, Tekscan, Inc). A repeated-measures ANOVA was used to test for differences in VO2 and vGRF between M and NM and across speeds. Significance was set at P < 0.05. RESULTS: Most subjects were unable to exercise for 5 min at treadmill speeds above 1.79 m/s in the NM mode; however, vGRF data were obtained for all subjects at each speed in both modes. VO2 was approx.40% higher during NM than M exercise across treadmill speeds. vGRF increased with treadmill speed but was not different between modes. CONCLUSION: Higher VO2 with no change in vGRF suggests that the additional metabolic cost associated with NM treadmill exercise is accounted for in the horizontal forces required to move the treadmill belt. Although this may limit the exercise duration at faster speeds, high-intensity NM exercise activates the hamstrings and plantarflexors, which are not specifically targeted or well protected by other in-flight countermeasures.

Asymmetric material impact: Achieving free surfaces velocities nearly double that of the projectile

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

Aslam, Tariq; Dattelbaum, Dana; Gustavsen, Richard

Hypervelocity impact speeds are often limited by practical considerations in guns and explosive driven systems. In particular, for gas guns (both powder driven and light gas guns), there is the general trend that higher projectile speeds often come at the expense of smaller diameters, and thus less time for examining shock phenomena prior to two dimensional release waves affecting the observed quantities of interest. Similarly, explosive driven systems have their own set of limiting conditions due to limitations in explosive energy and size of devices required as engineering dimensions increase. The focus in this study is to present a methodologymore » of obtaining free surface velocities well in excess of the projectile velocity. The key to this approach is in using a high impedance projectile that impacts a series of progressively lower impedance materials. The free surface velocity (if they were separated) of each of the progressively lower impedance materials would increase for each material. The theory behind this approach, as well as experimental results are presented.« less

Asymmetric material impact: Achieving free surfaces velocities nearly double that of the projectile

DOE PAGES

Aslam, Tariq; Dattelbaum, Dana; Gustavsen, Richard; ...

2015-05-19

Hypervelocity impact speeds are often limited by practical considerations in guns and explosive driven systems. In particular, for gas guns (both powder driven and light gas guns), there is the general trend that higher projectile speeds often come at the expense of smaller diameters, and thus less time for examining shock phenomena prior to two dimensional release waves affecting the observed quantities of interest. Similarly, explosive driven systems have their own set of limiting conditions due to limitations in explosive energy and size of devices required as engineering dimensions increase. The focus in this study is to present a methodologymore » of obtaining free surface velocities well in excess of the projectile velocity. The key to this approach is in using a high impedance projectile that impacts a series of progressively lower impedance materials. The free surface velocity (if they were separated) of each of the progressively lower impedance materials would increase for each material. The theory behind this approach, as well as experimental results are presented.« less

32 CFR 263.6 - Speeding or reckless driving.

Code of Federal Regulations, 2012 CFR

2012-07-01

..., weather, and road surface and having regard to the actual and potential hazards existing. (b) Except when a special hazard exists that requires lower speed, the speed limit on the site is 15 m.p.h., unless another speed limit has been duly posted, and no person shall drive a motor vehicle on the site in excess...

32 CFR 263.6 - Speeding or reckless driving.

Code of Federal Regulations, 2014 CFR

2014-07-01

..., weather, and road surface and having regard to the actual and potential hazards existing. (b) Except when a special hazard exists that requires lower speed, the speed limit on the site is 15 m.p.h., unless another speed limit has been duly posted, and no person shall drive a motor vehicle on the site in excess...

32 CFR 263.6 - Speeding or reckless driving.

Code of Federal Regulations, 2010 CFR

2010-07-01

..., weather, and road surface and having regard to the actual and potential hazards existing. (b) Except when a special hazard exists that requires lower speed, the speed limit on the site is 15 m.p.h., unless another speed limit has been duly posted, and no person shall drive a motor vehicle on the site in excess...

32 CFR 263.6 - Speeding or reckless driving.

Code of Federal Regulations, 2011 CFR

2011-07-01

..., weather, and road surface and having regard to the actual and potential hazards existing. (b) Except when a special hazard exists that requires lower speed, the speed limit on the site is 15 m.p.h., unless another speed limit has been duly posted, and no person shall drive a motor vehicle on the site in excess...

32 CFR 263.6 - Speeding or reckless driving.

Code of Federal Regulations, 2013 CFR

2013-07-01

..., weather, and road surface and having regard to the actual and potential hazards existing. (b) Except when a special hazard exists that requires lower speed, the speed limit on the site is 15 m.p.h., unless another speed limit has been duly posted, and no person shall drive a motor vehicle on the site in excess...

77 FR 69572 - Special Conditions: Embraer S.A., Model EMB-550 Airplanes; Flight Envelope Protection: High Speed...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-11-20

... Envelope Protection: High Speed Limiting AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice... inadvertently or intentionally exceeding a speed approximately equivalent to V FC or attaining V DF . Current Title 14 Code of Federal Regulations (14 CFR) part 25 do not relate to a high speed limiter that might...

Higher-than-predicted saltation threshold wind speeds on Titan.

PubMed

Burr, Devon M; Bridges, Nathan T; Marshall, John R; Smith, James K; White, Bruce R; Emery, Joshua P

2015-01-01

Titan, the largest satellite of Saturn, exhibits extensive aeolian, that is, wind-formed, dunes, features previously identified exclusively on Earth, Mars and Venus. Wind tunnel data collected under ambient and planetary-analogue conditions inform our models of aeolian processes on the terrestrial planets. However, the accuracy of these widely used formulations in predicting the threshold wind speeds required to move sand by saltation, or by short bounces, has not been tested under conditions relevant for non-terrestrial planets. Here we derive saltation threshold wind speeds under the thick-atmosphere, low-gravity and low-sediment-density conditions on Titan, using a high-pressure wind tunnel refurbished to simulate the appropriate kinematic viscosity for the near-surface atmosphere of Titan. The experimentally derived saltation threshold wind speeds are higher than those predicted by models based on terrestrial-analogue experiments, indicating the limitations of these models for such extreme conditions. The models can be reconciled with the experimental results by inclusion of the extremely low ratio of particle density to fluid density on Titan. Whereas the density ratio term enables accurate modelling of aeolian entrainment in thick atmospheres, such as those inferred for some extrasolar planets, our results also indicate that for environments with high density ratios, such as in jets on icy satellites or in tenuous atmospheres or exospheres, the correction for low-density-ratio conditions is not required.

Characterization and Impact of Low Frequency Wind Turbine Noise Emissions

NASA Astrophysics Data System (ADS)

Finch, James

Wind turbine noise is a complex issue that requires due diligence to minimize any potential impact on quality of life. This study enhances existing knowledge of wind turbine noise through focused analyses of downwind sound propagation, directionality, and the low frequency component of the noise. Measurements were conducted at four wind speeds according to a design of experiments at incremental distances and angles. Wind turbine noise is shown to be highly directional, while downwind sound propagation is spherical with limited ground absorption. The noise is found to have a significant low frequency component that is largely independent of wind speed over the 20-250 Hz range. The generated low frequency noise is shown to be audible above 40 Hz at the MOE setback distance of 550 m. Infrasound levels exhibit higher dependency on wind speed, but remain below audible levels up to 15 m/s.

Effectiveness of transverse grooves in rigid pavement

NASA Astrophysics Data System (ADS)

Gurney, G. F.; Bryden, J. E.

1982-10-01

Transverse grooves were installed at 11 intersection approaches on worn rigid pavement to reduce a high rate of wet road accidents. In most cases, accident reductions were experienced only at intersections with multiple negative operational characteristics, including higher approach speeds, limited sight distances, and frequent vehicle stopping for turns or stop signs. Intersections with no more than one negative characteristic generally did not benefit from grooving.

Comparative analysis of speed's impact on muscle demands during partial body weight support motor-assisted elliptical training.

PubMed

Burnfield, Judith M; Irons, Sonya L; Buster, Thad W; Taylor, Adam P; Hildner, Gretchen A; Shu, Yu

2014-01-01

Individuals with walking limitations often experience challenges engaging in functionally relevant exercise. An adapted elliptical trainer (motor to assist pedal movement, integrated body weight harness, ramps/stairs, and grab rails) has been developed to help individuals with physical disabilities and chronic conditions regain/retain walking capacity and fitness. However, limited published studies are available to guide therapeutic interventions. This repeated measures study examined the influence of motor-assisted elliptical training speed on lower extremity muscle demands at four body weight support (BWS) levels commonly used therapeutically for walking. Electromyography (EMG) and pedal trajectory data were recorded as ten individuals without known disability used the motor-assisted elliptical trainer at three speeds [20,40, 60 revolutions per minute (RPM)] during each BWS level (0%, 20%, 40%, 60%). Overall, the EMG activity (peak, mean, duration) in key stabilizer muscles (i.e., gluteus medius, gluteus maximus, vastus lateralis, medial gastrocnemius and soleus) recorded at 60 RPM exceeded those at 40 RPM, which were higher than values at 20 RPM in all but three situations (gluteus medius mean at 0% BWS, vastus lateralis mean at 20% BWS, soleus duration at 40% BWS); however, these differences did not always achieve statistical significance. Slower motor-assisted speeds can be used to accommodate weakness of gluteus medius, gluteus maximus, vastus lateralis, medial gastrocnemius and soleus. As strength improves, training at faster motor-assisted speeds may provide a means to progressively challenge key lower extremity stabilizers. Copyright © 2013 Elsevier B.V. All rights reserved.

Evaluation of electronic speed limit signs on US 30.

DOT National Transportation Integrated Search

2011-09-01

This study documents the speed : reduction impacts of two dynamic, : electronic school zone speed limit signs : at United Community Schools between : Ames and Boone, Iowa. The school : facility is situated along US Highway 30, : a rural four-lane div...

Evaluation of variable advisory speed limits in work zones.

DOT National Transportation Integrated Search

2013-08-01

Variable advisory speed limit (VASL) systems could be effective at both urban and rural work zones, at both uncongested and congested sites. At uncongested urban work zones, the average speeds with VASL were lower than without VASL. But the standard ...

Safety impacts of different speed limits on cars and trucks : final report

DOT National Transportation Integrated Search

1994-05-01

The objectives of this study were to determine whether differential or uniform speed limits are more beneficial to transportation safety and traffic operations on Interstate highways. The approach to achieving this objective was to examine speed and ...

Using road markings as a continuous cue for speed choice.

PubMed

Charlton, Samuel G; Starkey, Nicola J; Malhotra, Neha

2018-08-01

The potential for using road markings to indicate speed limits was investigated in a driving simulator over the course of two sessions. Two types of experimental road markings, an "Attentional" set designed to provide visually distinct cues to indicate speed limits of 60, 80 and 100 km/h, and a "Perceptual" set designed to also affect drivers' perception of speed, were compared to a standard undifferentiated set of markings. Participants (n = 20 per group) were assigned to one of four experimental groups (Attentional-Explicit, Attentional-Implicit, Perceptual-Explicit, Perceptual-Implicit) or a Control group (n = 22; standard road markings). The Explicit groups were instructed about the meaning of the road markings while those in the Implicit and Control groups did not receive any explanation. Participants drove five 10 km simulated roads containing three speed zones (60, 80 and 100 km/h) during the first session. The participants returned to the laboratory approximately 3 days later to drive five more trials including roads they had not seen before, a trial that included a secondary task, and a trial where speed signs were removed and only markings were present. The findings indicated that both types of road markings improved drivers' compliance with speed limits compared to the control group, but that explicit instruction as to the meaning of the markings was needed to realise their full benefit. Although previous research has indicated the benefit of road markings used as warnings to indicate speed reductions in advance of horizontal or vertical curves, the findings of the present experiment also suggest that systematically associating road markings with specific speed limits may be a useful way to improve speed limit compliance and increase speed homogeneity. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

Rapid assessment of road safety policy change: relaxation of the national speed enforcement law in Russia leads to large increases in the prevalence of speeding.

PubMed

Bhalla, Kavi; Paichadze, Nino; Gupta, Shivam; Kliavin, Vladimir; Gritsenko, Elena; Bishai, David; Hyder, Adnan A

2015-02-01

Reducing vehicle speed is among the most effective road safety strategies. We assess how a new policy in Russia that eliminates fines for driving up to 20 km/h above the speed limit has affected the prevalence of speeding. We measured speeds periodically in 13 districts of two Russian regions during 2011-2013 and analysed the effect of the policy using difference-in-differences to control for seasonality. We find that the prevalence of speeding was declining steadily but half of the gains since mid-2011 were lost immediately after the new policy. Overall speeding increased significantly by 13 percentage points (pp, 95% CI 4 to 19). Speeding more than 10 km/h above the limit increased significantly by 10 pp (95% CI 2 to 12), and extreme speeding increased but not significantly (1.7 pp, 95% CI -1.1 to 4.5). Road traffic injuries will likely increase in Russia unless speeding fines are reinstated. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Status report on the effects of the 65 mph speed limit on Virginia's rural interstate highway system : submitted to the Secretary of Transportation and Public Safety from the Secretarial Task Force on Interstate Highway Speed limits.

DOT National Transportation Integrated Search

1989-01-01

In 1987, the Secretary of Transportation and Public Safety created a task force to study the potential effects of raising the speed limit on rural interstate highways in Virginia. In its 1988 session, the Virginia General Assembly passed legislation ...

Relationships Between Performance on Assessments of Executive Function and Fall Risk Screening Measures in Community-Dwelling Older Adults.

PubMed

Blackwood, Jennifer; Shubert, Tiffany; Forgarty, Kieran; Chase, Carla

2016-01-01

Fall-related injuries are a leading cause of institutionalization and morbidity in older adults. Limitations in cognition, including deficits in higher cognitive processes, like executive function (EF), contribute to a higher risk of falling in older adults. Specifically, declines in EF have been associated with changes in gait, limited mobility, and an increased frequency of falling. It is unknown whether associations between performance on commonly used clinical assessments of EF and performance on commonly used physical performance measures of fall risk are present. The purpose of this study was to examine the relationship between a clinical measure of EF, the Trail Making Test Part B (TMT-B), and 3 physical performance measures of fall risk: the Timed Up and Go (TUG) test, gait speed, and the Five Times Sit to Stand (FTSTS) test, in a group of community-dwelling older adults. Forty-seven community-dwelling older adults met the inclusion/exclusion criteria. Demographic information was obtained and measures of fall risk and cognition were performed. Correlations and linear regression analyses to assess relationships between measures were completed. To account for the high prevalence of mild cognitive impairment (MCI) in this population, the sample was screened and stratified for MCI in post hoc analyses. The EF performance was not significantly correlated with performance on the FTSTS test (ρ = 0.26, P > .05) but was significantly correlated with the TUG test (ρ = 0.31, P < .05) and gait speed (r = -0.36, P < .05). These relationships remained after adjusting for age and education in multivariate models. Results from post hoc analyses demonstrated that only those with MCI had significant relationships between EF and physical performance measures. TMT-B scores in the MCI group were significantly correlated with gait speed (ρ = -0.51, P < .05) and TUG test (ρ = 0.58, P < .05). A significant relationship exists between performance on clinical assessments of EF and fall risk assessments that integrate a mobility task for those individuals who screen positive for MCI. For those who screened negative, no significant relationship exists. Given the large prevalence of undiagnosed MCI in community-dwelling older adults, this finding could be used as an indication to screen older adults for MCI. Screening tools that require cognitive resources such as gait speed appear to have significant relationships with performance of EF for those who screen positive for MCI. This information could be used clinically to identify older adults with cognitive limitations, which could put them at higher risk for falling.

14 CFR 25.1515 - Landing gear speeds.

Code of Federal Regulations, 2013 CFR

2013-01-01

... Limitations § 25.1515 Landing gear speeds. (a) The established landing gear operating speed or speeds, V LO... retraction speed, the two speeds must be designated as V LO(EXT) and V LO(RET), respectively. (b) The...

14 CFR 25.1515 - Landing gear speeds.

Code of Federal Regulations, 2012 CFR

2012-01-01

... Limitations § 25.1515 Landing gear speeds. (a) The established landing gear operating speed or speeds, V LO... retraction speed, the two speeds must be designated as V LO(EXT) and V LO(RET), respectively. (b) The...

14 CFR 25.1515 - Landing gear speeds.

Code of Federal Regulations, 2010 CFR

2010-01-01

... Limitations § 25.1515 Landing gear speeds. (a) The established landing gear operating speed or speeds, V LO... retraction speed, the two speeds must be designated as V LO(EXT) and V LO(RET), respectively. (b) The...

14 CFR 25.1515 - Landing gear speeds.

Code of Federal Regulations, 2011 CFR

2011-01-01

... Limitations § 25.1515 Landing gear speeds. (a) The established landing gear operating speed or speeds, V LO... retraction speed, the two speeds must be designated as V LO(EXT) and V LO(RET), respectively. (b) The...

14 CFR 25.1515 - Landing gear speeds.

Code of Federal Regulations, 2014 CFR

2014-01-01

... Limitations § 25.1515 Landing gear speeds. (a) The established landing gear operating speed or speeds, V LO... retraction speed, the two speeds must be designated as V LO(EXT) and V LO(RET), respectively. (b) The...

Teleseismic P wave tomography of South Island, New Zealand upper mantle: Evidence of subduction of Pacific lithosphere since 45 Ma

NASA Astrophysics Data System (ADS)

Zietlow, Daniel W.; Molnar, Peter H.; Sheehan, Anne F.

2016-06-01

A P wave speed tomogram produced from teleseismic travel time measurements made on and offshore the South Island of New Zealand shows a nearly vertical zone with wave speeds that are 4.5% higher than the background average reaching to depths of approximately 450 km under the northwestern region of the island. This structure is consistent with oblique west-southwest subduction of Pacific lithosphere since about 45 Ma, when subduction beneath the region began. The high-speed zone reaches about 200-300 km below the depths of the deepest intermediate-depth earthquakes (subcrustal to ~200 km) and therefore suggests that ~200-300 km of slab below them is required to produce sufficient weight to induce the intermediate-depth seismicity. In the southwestern South Island, high P wave speeds indicate subduction of the Australian plate at the Puysegur Trench to approximately 200 km depth. A band with speeds ~2-3.5% lower than the background average is found along the east coast of the South Island to depths of ~150-200 km and underlies Miocene or younger volcanism; these low speeds are consistent with thinned lithosphere. A core of high speeds under the Southern Alps associated with a convergent margin and mountain building imaged in previous investigations is not well resolved in this study. This could suggest that such high speeds are limited in both width and depth and not resolvable by our data.

Evaluating the impacts of speed limit policy alternatives.

DOT National Transportation Integrated Search

2014-07-01

As of June 2014, Michigan is one of eight states with a differential speed limit in place on its rural : freeways, which sets a maximum speed of 70 mph for passenger vehicles and 60 mph for trucks and : buses. In select urban environments, these spee...

The impact of the 65 MPH speed limit on Virginia's rural interstate highways through 1990.

DOT National Transportation Integrated Search

1992-01-01

In April of 1987, Congress passed the Surface Transportation and Uniform Relocation Assistance Act (STURAA), which permitted states to raise their maximum speed limit on rural interstate highways (rural interstates) to 65 mph. Virginia's 65 mph speed...

In-Situ Determination of the Mechanical Properties of Gliding or Non-Motile Bacteria by Atomic Force Microscopy under Physiological Conditions without Immobilization

PubMed Central

Dhahri, Samia; Ramonda, Michel; Marlière, Christian

2013-01-01

We present a study about AFM imaging of living, moving or self-immobilized bacteria in their genuine physiological liquid medium. No external immobilization protocol, neither chemical nor mechanical, was needed. For the first time, the native gliding movements of Gram-negative Nostoc cyanobacteria upon the surface, at speeds up to 900 µm/h, were studied by AFM. This was possible thanks to an improved combination of a gentle sample preparation process and an AFM procedure based on fast and complete force-distance curves made at every pixel, drastically reducing lateral forces. No limitation in spatial resolution or imaging rate was detected. Gram-positive and non-motile Rhodococcus wratislaviensis bacteria were studied as well. From the approach curves, Young modulus and turgor pressure were measured for both strains at different gliding speeds and are ranging from 20±3 to 105±5 MPa and 40±5 to 310±30 kPa depending on the bacterium and the gliding speed. For Nostoc, spatially limited zones with higher values of stiffness were observed. The related spatial period is much higher than the mean length of Nostoc nodules. This was explained by an inhomogeneous mechanical activation of nodules in the cyanobacterium. We also observed the presence of a soft extra cellular matrix (ECM) around the Nostoc bacterium. Both strains left a track of polymeric slime with variable thicknesses. For Rhodococcus, it is equal to few hundreds of nanometers, likely to promote its adhesion to the sample. While gliding, the Nostoc secretes a slime layer the thickness of which is in the nanometer range and increases with the gliding speed. This result reinforces the hypothesis of a propulsion mechanism based, for Nostoc cyanobacteria, on ejection of slime. These results open a large window on new studies of both dynamical phenomena of practical and fundamental interests such as the formation of biofilms and dynamic properties of bacteria in real physiological conditions. PMID:23593493

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

Hessell, Steven M.; Morris, Robert L.; McGrogan, Sean W.

A powertrain including an engine and torque machines is configured to transfer torque through a multi-mode transmission to an output member. A method for controlling the powertrain includes employing a closed-loop speed control system to control torque commands for the torque machines in response to a desired input speed. Upon approaching a power limit of a power storage device transferring power to the torque machines, power limited torque commands are determined for the torque machines in response to the power limit and the closed-loop speed control system is employed to determine an engine torque command in response to the desiredmore » input speed and the power limited torque commands for the torque machines.« less

[Effects of wind speed on drying processes of fuelbeds composed of Mongolian oak broad-leaves.

PubMed

Zhang, Li Bin; Sun, Ping; Jin, Sen

2016-11-18

Water desorption processes of fuel beds with Mongolian oak broad-leaves were observed under conditions with various wind speeds but nearly constant air temperature and humidity. The effects of wind speed on drying coefficients of fuel beds with various moisture contents were analyzed. Three phases of drying process, namely high initial moisture content (>75%) of phase 1, transition state of phase 2, and equilibrium phase III could be identified. During phase 1, water loss rate under higher wind speed was higher than that under lower wind speed. Water loss rate under higher wind speed was lower than that under lower wind speed during phase 2. During phase 3, water loss rates under different wind speeds were similar. The wind effects decreased with the decrease of fuel moisture. The drying coefficient of the Mongolian oak broad-leaves fuel beds was affected by wind speed and fuel bed compactness, and the interaction between these two factors. The coefficient increased with wind speed roughly in a monotonic cubic polynomial form.

Two-Stage Centrifugal Fan

NASA Technical Reports Server (NTRS)

Converse, David

2011-01-01

Fan designs are often constrained by envelope, rotational speed, weight, and power. Aerodynamic performance and motor electrical performance are heavily influenced by rotational speed. The fan used in this work is at a practical limit for rotational speed due to motor performance characteristics, and there is no more space available in the packaging for a larger fan. The pressure rise requirements keep growing. The way to ordinarily accommodate a higher DP is to spin faster or grow the fan rotor diameter. The invention is to put two radially oriented stages on a single disk. Flow enters the first stage from the center; energy is imparted to the flow in the first stage blades, the flow is redirected some amount opposite to the direction of rotation in the fixed stators, and more energy is imparted to the flow in the second- stage blades. Without increasing either rotational speed or disk diameter, it is believed that as much as 50 percent more DP can be achieved with this design than with an ordinary, single-stage centrifugal design. This invention is useful primarily for fans having relatively low flow rates with relatively high pressure rise requirements.

Feature-fused SSD: fast detection for small objects

NASA Astrophysics Data System (ADS)

Cao, Guimei; Xie, Xuemei; Yang, Wenzhe; Liao, Quan; Shi, Guangming; Wu, Jinjian

2018-04-01

Small objects detection is a challenging task in computer vision due to its limited resolution and information. In order to solve this problem, the majority of existing methods sacrifice speed for improvement in accuracy. In this paper, we aim to detect small objects at a fast speed, using the best object detector Single Shot Multibox Detector (SSD) with respect to accuracy-vs-speed trade-off as base architecture. We propose a multi-level feature fusion method for introducing contextual information in SSD, in order to improve the accuracy for small objects. In detailed fusion operation, we design two feature fusion modules, concatenation module and element-sum module, different in the way of adding contextual information. Experimental results show that these two fusion modules obtain higher mAP on PASCAL VOC2007 than baseline SSD by 1.6 and 1.7 points respectively, especially with 2-3 points improvement on some small objects categories. The testing speed of them is 43 and 40 FPS respectively, superior to the state of the art Deconvolutional single shot detector (DSSD) by 29.4 and 26.4 FPS.

Snakes mimic earthworms: propulsion using rectilinear travelling waves

PubMed Central

Marvi, Hamidreza; Bridges, Jacob; Hu, David L.

2013-01-01

In rectilinear locomotion, snakes propel themselves using unidirectional travelling waves of muscular contraction, in a style similar to earthworms. In this combined experimental and theoretical study, we film rectilinear locomotion of three species of snakes, including red-tailed boa constrictors, Dumeril's boas and Gaboon vipers. The kinematics of a snake's extension–contraction travelling wave are characterized by wave frequency, amplitude and speed. We find wave frequency increases with increasing body size, an opposite trend than that for legged animals. We predict body speed with 73–97% accuracy using a mathematical model of a one-dimensional n-linked crawler that uses friction as the dominant propulsive force. We apply our model to show snakes have optimal wave frequencies: higher values increase Froude number causing the snake to slip; smaller values decrease thrust and so body speed. Other choices of kinematic variables, such as wave amplitude, are suboptimal and appear to be limited by anatomical constraints. Our model also shows that local body lifting increases a snake's speed by 31 per cent, demonstrating that rectilinear locomotion benefits from vertical motion similar to walking. PMID:23635494

The Association between Regional Environmental Factors and Road Trauma Rates: A Geospatial Analysis of 10 Years of Road Traffic Crashes in British Columbia, Canada

PubMed Central

Brubacher, Jeffrey R.; Chan, Herbert; Erdelyi, Shannon; Schuurman, Nadine; Amram, Ofer

2016-01-01

Background British Columbia, Canada is a geographically large jurisdiction with varied environmental and socio-cultural contexts. This cross-sectional study examined variation in motor vehicle crash rates across 100 police patrols to investigate the association of crashes with key explanatory factors. Methods Eleven crash outcomes (total crashes, injury crashes, fatal crashes, speed related fatal crashes, total fatalities, single-vehicle night-time crashes, rear-end collisions, and collisions involving heavy vehicles, pedestrians, cyclists, or motorcyclists) were identified from police collision reports and insurance claims and mapped to police patrols. Six potential explanatory factors (intensity of traffic law enforcement, speed limits, climate, remoteness, socio-economic factors, and alcohol consumption) were also mapped to police patrols. We then studied the association between crashes and explanatory factors using negative binomial models with crash count per patrol as the response variable and explanatory factors as covariates. Results Between 2003 and 2012 there were 1,434,239 insurance claim collisions, 386,326 police reported crashes, and 3,404 fatal crashes. Across police patrols, there was marked variation in per capita crash rate and in potential explanatory factors. Several factors were associated with crash rates. Percent roads with speed limits ≤ 60 km/hr was positively associated with total crashes, injury crashes, rear end collisions, and collisions involving pedestrians, cyclists, and heavy vehicles; and negatively associated with single vehicle night-time crashes, fatal crashes, fatal speeding crashes, and total fatalities. Higher winter temperature was associated with lower rates of overall collisions, single vehicle night-time collisions, collisions involving heavy vehicles, and total fatalities. Lower socio-economic status was associated with higher rates of injury collisions, pedestrian collisions, fatal speeding collisions, and fatal collisions. Regions with dedicated traffic officers had fewer fatal crashes and fewer fatal speed related crashes but more rear end crashes and more crashes involving cyclists or pedestrians. The number of traffic citations per 1000 drivers was positively associated with total crashes, fatal crashes, total fatalities, fatal speeding crashes, injury crashes, single vehicle night-time crashes, and heavy vehicle crashes. Possible explanations for these associations are discussed. Conclusions There is wide variation in per capita rates of motor vehicle crashes across BC police patrols. Some variation is explained by factors such as climate, road type, remoteness, socioeconomic variables, and enforcement intensity. The ability of explanatory factors to predict crash rates would be improved if considered with local traffic volume by all travel modes. PMID:27099930

Flight and Test-stand Investigation of High-performance Fuels in Modified Double-row Radial Air-cooled Engines III: Knock-limited Performance of 33-R as Compared with a Triptane Blend and 28-R in Flight

NASA Technical Reports Server (NTRS)

Blackman, Calvin C.; White, H. Jack

1945-01-01

A comparison has been made in flight of the antiknock characteristics of 33-R fuel with that of 28-R and a triptane blent. The knock-limited performance of the three fuels - 33-R, a blend of 80 percent 28-R plus 20 percent triptane (leaded to 4.5 ml TEL/gal), and 28-R - was investigated in two modified 14-cylinder double-row radial air-cooled engines. Tests were conducted on the engines as installed in the left inboard nacelle of an airplane. A carburetor-air temperature of approximately 85 deg F was maintained. The conditions covered at an engine speed of 2250 rpm were high and low blower ratios and spark advances of 25 deg and 32 deg B.T.C. For an engine speed of 1800 rpm only the high-blower condition was investigated for both 25 deg and 32 deg spark advances. For the conditions investigated the difference between 33-R and the triptane blend was found to be slight; the performance of 33-R fuel, however, was slightly higher than that of the triptane blend in the lean region. The knock-limited power obtained with the 33-R fuel was from 14 to 28 percent higher than that of the 28-R fuel for the entire range of test conditions; the greatest improvement was shown in the lean region.

Evaluation of the Impacts of Differential Speed Limits on Interstate Highways in Idaho

DOT National Transportation Integrated Search

2012-10-01

In this research, an evaluation of the impacts of differential speed limits on rural interstate highways in Idaho was completed. The main purpose for this research was to determine if there have been any speed or safety effects after enacting the DSL...

Routine and active metabolic rates of migrating adult wild sockeye salmon (Oncorhynchus nerka Walbaum) in seawater and freshwater.

PubMed

Wagner, G N; Kuchel, L J; Lotto, A; Patterson, D A; Shrimpton, J M; Hinch, S G; Farrell, A P

2006-01-01

We present the first data on the differences in routine and active metabolic rates for sexually maturing migratory adult sockeye salmon (Oncorhynchus nerka) that were intercepted in the ocean and then held in either seawater or freshwater. Routine and active oxygen uptake rates (MO2) were significantly higher (27%-72%) in seawater than in freshwater at all swimming speeds except those approaching critical swimming speed. During a 45-min recovery period, the declining postexercise oxygen uptake remained 58%-73% higher in seawater than in freshwater. When fish performed a second swim test, active metabolic rates again remained 28%-81% higher for fish in seawater except at the critical swimming speed. Despite their differences in metabolic rates, fish in both seawater and freshwater could repeat the swim test and reach a similar maximum oxygen uptake and critical swimming speed as in the first swim test, even without restoring routine metabolic rate between swim tests. Thus, elevated MO2 related to either being in seawater as opposed to freshwater or not being fully recovered from previous exhaustive exercise did not present itself as a metabolic loading that limited either critical swimming performance or maximum MO2. The basis for the difference in metabolic rates of migratory sockeye salmon held in seawater and freshwater is uncertain, but it could include differences in states of nutrition, reproduction, and restlessness, as well as ionic differences. Regardless, this study elucidates some of the metabolic costs involved during the migration of adult salmon from seawater to freshwater, which may have applications for fisheries conservation and management models of energy use.

Limits and signatures of relativistic spaceflight

NASA Astrophysics Data System (ADS)

Yurtsever, Ulvi; Wilkinson, Steven

2018-01-01

While special relativity imposes an absolute speed limit at the speed of light, our Universe is not empty Minkowski spacetime. The constituents that fill the interstellar/intergalactic vacuum, including the cosmic microwave background photons, impose a lower speed limit on any object travelling at relativistic velocities. Scattering of cosmic microwave photons from an ultra-relativistic object may create radiation with a characteristic signature allowing the detection of such objects at large distances.

Generalized Geometric Quantum Speed Limits

NASA Astrophysics Data System (ADS)

Pires, Diego Paiva; Cianciaruso, Marco; Céleri, Lucas C.; Adesso, Gerardo; Soares-Pinto, Diogo O.

2016-04-01

The attempt to gain a theoretical understanding of the concept of time in quantum mechanics has triggered significant progress towards the search for faster and more efficient quantum technologies. One of such advances consists in the interpretation of the time-energy uncertainty relations as lower bounds for the minimal evolution time between two distinguishable states of a quantum system, also known as quantum speed limits. We investigate how the nonuniqueness of a bona fide measure of distinguishability defined on the quantum-state space affects the quantum speed limits and can be exploited in order to derive improved bounds. Specifically, we establish an infinite family of quantum speed limits valid for unitary and nonunitary evolutions, based on an elegant information geometric formalism. Our work unifies and generalizes existing results on quantum speed limits and provides instances of novel bounds that are tighter than any established one based on the conventional quantum Fisher information. We illustrate our findings with relevant examples, demonstrating the importance of choosing different information metrics for open system dynamics, as well as clarifying the roles of classical populations versus quantum coherences, in the determination and saturation of the speed limits. Our results can find applications in the optimization and control of quantum technologies such as quantum computation and metrology, and might provide new insights in fundamental investigations of quantum thermodynamics.

Speed control system for an access gate

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

Bzorgi, Fariborz M

2012-03-20

An access control apparatus for an access gate. The access gate typically has a rotator that is configured to rotate around a rotator axis at a first variable speed in a forward direction. The access control apparatus may include a transmission that typically has an input element that is operatively connected to the rotator. The input element is generally configured to rotate at an input speed that is proportional to the first variable speed. The transmission typically also has an output element that has an output speed that is higher than the input speed. The input element and the outputmore » element may rotate around a common transmission axis. A retardation mechanism may be employed. The retardation mechanism is typically configured to rotate around a retardation mechanism axis. Generally the retardation mechanism is operatively connected to the output element of the transmission and is configured to retard motion of the access gate in the forward direction when the first variable speed is above a control-limit speed. In many embodiments the transmission axis and the retardation mechanism axis are substantially co-axial. Some embodiments include a freewheel/catch mechanism that has an input connection that is operatively connected to the rotator. The input connection may be configured to engage an output connection when the rotator is rotated at the first variable speed in a forward direction and configured for substantially unrestricted rotation when the rotator is rotated in a reverse direction opposite the forward direction. The input element of the transmission is typically operatively connected to the output connection of the freewheel/catch mechanism.« less

Automatic film processors' quality control test in Greek military hospitals.

PubMed

Lymberis, C; Efstathopoulos, E P; Manetou, A; Poudridis, G

1993-04-01

The two major military radiology installations (Athens, Greece) using a total of 15 automatic film processors were assessed using the 21-step-wedge method. The results of quality control in all these processors are presented. The parameters measured under actual working conditions were base and fog, contrast and speed. Base and fog as well as speed displayed large variations with average values generally higher than acceptable, whilst contrast displayed greater stability. Developer temperature was measured daily during the test and was found to be outside the film manufacturers' recommended limits in nine of the 15 processors. In only one processor did film passing time vary on an every day basis and this was due to maloperation. Developer pH test was not part of the daily monitoring service being performed every 5 days for each film processor and found to be in the range 9-12; 10 of the 15 processors presented pH values outside the limits specified by the film manufacturers.

Comprehensive and human capital crash costs by maximum police-reported injury severity within selected crash types.

PubMed

Zaloshnja, Eduard; Miller, Ted; Council, Forrest; Persaud, Bhagwant

2004-01-01

This paper presents estimates for both the economic and comprehensive costs per crash for three police-coded severity groupings within 16 selected crash types and within two speed limit categories (or=50 mph). The economic costs are hard dollar costs. The comprehensive costs include economic costs and quality of life losses. We merged previously developed costs per victim keyed on the Abbreviated Injury Scale (AIS) into US crash data files that scored injuries in both the AIS and police-coded severity scales to produce per crash estimates. The most costly crashes were non-intersection fatal/disabling injury crashes on a road with a speed limit of 50 miles per hour or higher where multiple vehicles crashed head-on or a single vehicle struck a human (over 1.69 and $1.16 million per crash, respectively). The annual cost of police-reported run-off-road collisions, which include both rollovers and object impacts, represented 34% of total costs.

Comprehensive and Human Capital Crash Costs by Maximum Police-Reported Injury Severity Within Selected Crash Types

PubMed Central

Zaloshnja, Eduard; Miller, Ted; Council, Forrest; Persaud, Bhagwant

2004-01-01

This paper presents estimates for both the economic and comprehensive costs per crash for three police-coded severity groupings within 16 selected crash types and within two speed limit categories (<=45 and >=50 mph). The economic costs are hard dollar costs. The comprehensive costs include economic costs and quality of life losses. We merged previously developed costs per victim keyed on the Abbreviated Injury Scale (AIS) into US crash data files that scored injuries in both the AIS and police-coded severity scales to produce per crash estimates. The most costly crashes were non-intersection fatal/disabling injury crashes on a road with a speed limit of 50 miles per hour or higher where multiple vehicles crashed head-on or a single vehicle struck a human (over 1.69 and $1.16 million per crash, respectively). The annual cost of police-reported run-off-road collisions, which include both rollovers and object impacts, represented 34% of total costs. PMID:15319129

Finite Element Analysis in Concurrent Processing: Computational Issues

NASA Technical Reports Server (NTRS)

Sobieszczanski-Sobieski, Jaroslaw; Watson, Brian; Vanderplaats, Garrett

2004-01-01

The purpose of this research is to investigate the potential application of new methods for solving large-scale static structural problems on concurrent computers. It is well known that traditional single-processor computational speed will be limited by inherent physical limits. The only path to achieve higher computational speeds lies through concurrent processing. Traditional factorization solution methods for sparse matrices are ill suited for concurrent processing because the null entries get filled, leading to high communication and memory requirements. The research reported herein investigates alternatives to factorization that promise a greater potential to achieve high concurrent computing efficiency. Two methods, and their variants, based on direct energy minimization are studied: a) minimization of the strain energy using the displacement method formulation; b) constrained minimization of the complementary strain energy using the force method formulation. Initial results indicated that in the context of the direct energy minimization the displacement formulation experienced convergence and accuracy difficulties while the force formulation showed promising potential.

Design of voice coil motor dynamic focusing unit for a laser scanner

NASA Astrophysics Data System (ADS)

Lee, Moon G.; Kim, Gaeun; Lee, Chan-Woo; Lee, Soo-Hun; Jeon, Yongho

2014-04-01

Laser scanning systems have been used for material processing tasks such as welding, cutting, marking, and drilling. However, applications have been limited by the small range of motion and slow speed of the focusing unit, which carries the focusing optics. To overcome these limitations, a dynamic focusing system with a long travel range and high speed is needed. In this study, a dynamic focusing unit for a laser scanning system with a voice coil motor (VCM) mechanism is proposed to enable fast speed and a wide focusing range. The VCM has finer precision and higher speed than conventional step motors and a longer travel range than earlier lead zirconium titanate actuators. The system has a hollow configuration to provide a laser beam path. This also makes it compact and transmission-free and gives it low inertia. The VCM's magnetics are modeled using a permeance model. Its design parameters are determined by optimization using the Broyden-Fletcher-Goldfarb-Shanno method and a sequential quadratic programming algorithm. After the VCM is designed, the dynamic focusing unit is fabricated and assembled. The permeance model is verified by a magnetic finite element method simulation tool, Maxwell 2D and 3D, and by measurement data from a gauss meter. The performance is verified experimentally. The results show a resolution of 0.2 μm and travel range of 16 mm. These are better than those of conventional focusing systems; therefore, this focusing unit can be applied to laser scanning systems for good machining capability.

Design of voice coil motor dynamic focusing unit for a laser scanner.

PubMed

Lee, Moon G; Kim, Gaeun; Lee, Chan-Woo; Lee, Soo-Hun; Jeon, Yongho

2014-04-01

Laser scanning systems have been used for material processing tasks such as welding, cutting, marking, and drilling. However, applications have been limited by the small range of motion and slow speed of the focusing unit, which carries the focusing optics. To overcome these limitations, a dynamic focusing system with a long travel range and high speed is needed. In this study, a dynamic focusing unit for a laser scanning system with a voice coil motor (VCM) mechanism is proposed to enable fast speed and a wide focusing range. The VCM has finer precision and higher speed than conventional step motors and a longer travel range than earlier lead zirconium titanate actuators. The system has a hollow configuration to provide a laser beam path. This also makes it compact and transmission-free and gives it low inertia. The VCM's magnetics are modeled using a permeance model. Its design parameters are determined by optimization using the Broyden-Fletcher-Goldfarb-Shanno method and a sequential quadratic programming algorithm. After the VCM is designed, the dynamic focusing unit is fabricated and assembled. The permeance model is verified by a magnetic finite element method simulation tool, Maxwell 2D and 3D, and by measurement data from a gauss meter. The performance is verified experimentally. The results show a resolution of 0.2 μm and travel range of 16 mm. These are better than those of conventional focusing systems; therefore, this focusing unit can be applied to laser scanning systems for good machining capability.

Effect of speed limit increase on crash rate on rural two-lane highways in Louisiana.

DOT National Transportation Integrated Search

2006-08-01

This study investigated the impact of a speed limit increase on the crash rate on rural twolane roads in Louisiana. The Louisiana crash database for 1999-2004 was used to compare rates of different crash severities and types before and after a speed ...

36 CFR 1004.21 - Speed limits.

Code of Federal Regulations, 2012 CFR

2012-07-01

... of a vehicle on a Presidio Trust road. Signs indicating that vehicle speed is determined by the use... sections of Presidio Trust road under repair or construction. (3) 45 miles per hour: upon all other Presidio Trust roads. (b) The Board may designate a different speed limit upon any Presidio Trust road when...

36 CFR 1004.21 - Speed limits.

Code of Federal Regulations, 2011 CFR

2011-07-01

... of a vehicle on a Presidio Trust road. Signs indicating that vehicle speed is determined by the use... sections of Presidio Trust road under repair or construction. (3) 45 miles per hour: upon all other Presidio Trust roads. (b) The Board may designate a different speed limit upon any Presidio Trust road when...

36 CFR 1004.21 - Speed limits.

Code of Federal Regulations, 2014 CFR

2014-07-01

... of a vehicle on a Presidio Trust road. Signs indicating that vehicle speed is determined by the use... sections of Presidio Trust road under repair or construction. (3) 45 miles per hour: upon all other Presidio Trust roads. (b) The Board may designate a different speed limit upon any Presidio Trust road when...

36 CFR 1004.21 - Speed limits.

Code of Federal Regulations, 2010 CFR

2010-07-01

... of a vehicle on a Presidio Trust road. Signs indicating that vehicle speed is determined by the use... sections of Presidio Trust road under repair or construction. (3) 45 miles per hour: upon all other Presidio Trust roads. (b) The Board may designate a different speed limit upon any Presidio Trust road when...

Quantum speed limit for arbitrary initial states

PubMed Central

Zhang, Ying-Jie; Han, Wei; Xia, Yun-Jie; Cao, Jun-Peng; Fan, Heng

2014-01-01

The minimal time a system needs to evolve from an initial state to its one orthogonal state is defined as the quantum speed limit time, which can be used to characterize the maximal speed of evolution of a quantum system. This is a fundamental question of quantum physics. We investigate the generic bound on the minimal evolution time of the open dynamical quantum system. This quantum speed limit time is applicable to both mixed and pure initial states. We then apply this result to the damped Jaynes-Cummings model and the Ohimc-like dephasing model starting from a general time-evolution state. The bound of this time-dependent state at any point in time can be found. For the damped Jaynes-Cummings model, when the system starts from the excited state, the corresponding bound first decreases and then increases in the Markovian dynamics. While in the non-Markovian regime, the speed limit time shows an interesting periodic oscillatory behavior. For the case of Ohimc-like dephasing model, this bound would be gradually trapped to a fixed value. In addition, the roles of the relativistic effects on the speed limit time for the observer in non-inertial frames are discussed. PMID:24809395

Control of surface defects on plasma-MIG hybrid welds in cryogenic aluminum alloys

NASA Astrophysics Data System (ADS)

Lee, Hee-Keun; Chun, Kwang-San; Park, Sang-Hyeon; Kang, Chung-Yun

2015-07-01

Lately, high production rate welding processes for Al alloys, which are used as LNG FPSO cargo containment system material, have been developed to overcome the limit of installation and high rework rates. In particular, plasma-metal inert gas (MIG) hybrid (PMH) welding can be used to obtain a higher deposition rate and lower porosity, while facilitating a cleaning effect by preheating and post heating the wire and the base metal. However, an asymmetric undercut and a black-colored deposit are created on the surface of PMH weld in Al alloys. For controlling the surface defect formation, the wire feeding speed and nozzle diameter in the PMH weld was investigated through arc phenomena with high-speed imaging and metallurgical analysis.

Electron bulk speed lags the protons in the collisionless solar wind

NASA Astrophysics Data System (ADS)

Tong, Y.; Bale, S. D.; Salem, C. S.; Pulupa, M.

2017-12-01

We use a large, statistical set of in situ measurements of the solar wind electron distribution from the Wind/3DP instrument to show that the magnetic field-aligned core electron-proton drift speed tend to small values at high collisionality and asymptotes towards a large limiting value in the collisionless limit. This collisionless drift-limit, when normalized to the local Alfven speed is large and may drive instabilities.

Higher speed freight truck market analysis.

DOT National Transportation Integrated Search

2013-07-01

A market analysis was conducted on behalf of FRA to determine the viability for implementation of higher speed freight rail service in anticipation of high-speed passenger rail service on upgraded freight rail corridors. : The analysis focused on the...

Higher speed freight truck market analysis.

DOT National Transportation Integrated Search

2013-07-01

A market analysis was conducted on behalf of FRA to determine the viability for implementation of higher speed freight rail : service in anticipation of high-speed passenger rail service on upgraded freight rail corridors. : The analysis focused on t...

Effect of interactions between vehicles and pedestrians on fuel consumption and emissions

NASA Astrophysics Data System (ADS)

Li, Xiang; Sun, Jian-Qiao

2014-12-01

This paper presents a study of variations of fuel consumption and emissions of vehicles due to random street crossings of pedestrians. The pedestrian and vehicle movement models as well as the interaction model between the two entities are presented. Extensive numerical simulations of single and multiple cars are carried out to investigate the traffic flow rate, vehicle average speed, fuel consumption, CO, HC and NOx emissions. Generally more noncompliant road-crossings of pedestrians lead to higher level of fuel consumptions and emissions of vehicles, and the traffic situation can be improved by imposing higher vehicle speed limit to some extent. Different traffic characteristics in low and high vehicle density regions are studied. The traffic flow is more influenced by crossing pedestrians in the low vehicle density region, while in the high vehicle density region, the interactions among vehicles dominate. The main contribution of this paper lies in the qualitative analysis of the impact of the interactions between pedestrians and vehicles on the traffic, its energy economy and emissions.

Method for experimental investigation of transient operation on Laval test stand for model size turbines

NASA Astrophysics Data System (ADS)

Fraser, R.; Coulaud, M.; Aeschlimann, V.; Lemay, J.; Deschenes, C.

2016-11-01

With the growing proportion of inconstant energy source as wind and solar, hydroelectricity becomes a first class source of peak energy in order to regularize the grid. The important increase of start - stop cycles may then cause a premature ageing of runners by both a higher number of cycles in stress fluctuations and by reaching a higher stress level in absolute. Aiming to sustain good quality development on fully homologous scale model turbines, the Hydraulic Machines Laboratory (LAMH) of Laval University has developed a methodology to operate model size turbines on transient regimes such as start-up, stop or load rejection on its test stand. This methodology allows maintaining a constant head while the wicket gates are opening or closing in a representative speed on the model scale of what is made on the prototype. This paper first presents the opening speed on model based on dimensionless numbers, the methodology itself and its application. Then both its limitation and the first results using a bulb turbine are detailed.

Cruise noise of the 2/9th scale model of the Large-scale Advanced Propfan (LAP) propeller, SR-7A

NASA Technical Reports Server (NTRS)

Dittmar, James H.; Stang, David B.

1987-01-01

Noise data on the Large-scale Advanced Propfan (LAP) propeller model SR-7A were taken in the NASA Lewis Research Center 8 x 6 foot Wind Tunnel. The maximum blade passing tone noise first rises with increasing helical tip Mach number to a peak level, then remains the same or decreases from its peak level when going to higher helical tip Mach numbers. This trend was observed for operation at both constant advance ratio and approximately equal thrust. This noise reduction or, leveling out at high helical tip Mach numbers, points to the use of higher propeller tip speeds as a possible method to limit airplane cabin noise while maintaining high flight speed and efficiency. Projections of the tunnel model data are made to the full scale LAP propeller mounted on the test bed aircraft and compared with predictions. The prediction method is found to be somewhat conservative in that it slightly overpredicts the projected model data at the peak.

Cruise noise of the 2/9 scale model of the Large-scale Advanced Propfan (LAP) propeller, SR-7A

NASA Technical Reports Server (NTRS)

Dittmar, James H.; Stang, David B.

1987-01-01

Noise data on the Large-scale Advanced Propfan (LAP) propeller model SR-7A were taken in the NASA Lewis Research Center 8 x 6 foot Wind Tunnel. The maximum blade passing tone noise first rises with increasing helical tip Mach number to a peak level, then remains the same or decreases from its peak level when going to higher helical tip Mach numbers. This trend was observed for operation at both constant advance ratio and approximately equal thrust. This noise reduction or, leveling out at high helical tip Mach numbers, points to the use of higher propeller tip speeds as a possible method to limit airplane cabin noise while maintaining high flight speed and efficiency. Projections of the tunnel model data are made to the full scale LAP propeller mounted on the test bed aircraft and compared with predictions. The prediction method is found to be somewhat conservative in that it slightly overpredicts the projected model data at the peak.

Thermodynamic Cycle Analysis of Magnetohydrodynamic-Bypass Airbreathing Hypersonic Engines

NASA Technical Reports Server (NTRS)

Litchford, Ron J.; Bityurin, Valentine A.; Lineberry, John T.

1999-01-01

Established analyses of conventional ramjet/scramjet performance characteristics indicate that a considerable decrease in efficiency can be expected at off-design flight conditions. This can be explained, in large part, by the deterioration of intake mass flow and limited inlet compression at low flight speeds and by the onset of thrust degradation effects associated with increased burner entry temperature at high flight speeds. In combination, these effects tend to impose lower and upper Mach number limits for practical flight. It has been noted, however, that Magnetohydrodynamic (MHD) energy management techniques represent a possible means for extending the flight Mach number envelope of conventional engines. By transferring enthalpy between different stages of the engine cycle, it appears that the onset of thrust degradation may be delayed to higher flight speeds. Obviously, the introduction of additional process inefficiencies is inevitable with this approach, but it is believed that these losses are more than compensated through optimization of the combustion process. The fundamental idea is to use MHD energy conversion processes to extract and bypass a portion of the intake kinetic energy around the burner. We refer to this general class of propulsion system as an MHD-bypass engine. In this paper, we quantitatively assess the performance potential and scientific feasibility of MHD-bypass airbreathing hypersonic engines using ideal gasdynamics and fundamental thermodynamic principles.

Method and system for controlling a rotational speed of a rotor of a turbogenerator

DOEpatents

Stahlhut, Ronnie Dean; Vuk, Carl Thomas

2008-12-30

A system and method controls a rotational speed of a rotor or shaft of a turbogenerator in accordance with a present voltage level on a direct current bus. A lower threshold and a higher threshold are established for a speed of a rotor or shaft of a turbogenerator. A speed sensor determines speed data or a speed signal for the rotor or shaft associated with a turbogenerator. A voltage regulator adjusts a voltage level associated with a direct current bus within a target voltage range if the speed data or speed signal indicates that the speed is above the higher threshold or below the lower threshold.

Influence of material anisotropy on the hydroelastic response of composite plates in water

NASA Astrophysics Data System (ADS)

Akcabay, Deniz Tolga; Young, Yin Lu

2018-03-01

Flexible lightweight plate-like lifting surfaces in external flows have a diverse range of use from propelling and controlling marine and aerospace vehicles to converting wind and ocean energy to electrical energy. Design and analysis of such structures are complex for underwater applications where the water density is much higher than air. The hydrodynamic loads, which vary with the inflow speed, can significantly alter the dynamic response and stability. This paper focuses on the hydroelastic response of composite plates in water. The results show that the dynamics and stability of the structure can be significantly modified by taking advantage of the material anisotropic; on the contrary, careless composite material designs may lead to unwanted dynamic instability failures. The resonance frequencies, divergence speeds, and fluid loss coefficients change with material anisotropy and hydrodynamic loads. The resonance frequencies are much lower in water than in air. The critical divergence speed increases, if the principal fiber direction is oriented towards the inflow. Hydrodynamic damping is shown to be much higher than the material damping, and tend to increase with flow speed and to decrease with increasing modal frequency. The paper derives Response Amplitude Operators (RAOs) for sample composite plates in water and use them to predict the motion response when subject to stochastic flow excitations. We show how material anisotropy can be used to passively tailor the plate vibration response spectrum to limit or enhance flow-induced vibrations of the plate depending on the desired applications.

Gravitational radiation and the ultimate speed in Rosen's bimetric theory of gravity

NASA Technical Reports Server (NTRS)

Caves, C. M.

1980-01-01

In Rosen's bimetric theory of gravity the (local) speed of gravitational radiation is determined by the combined effects of cosmological boundary values and nearby concentrations of matter. It is possible for the speed of gravitational radiation to be less than the speed of light. It is here shown that the emission of gravitational radiation prevents particles of nonzero rest mass from exceeding the speed of gravitational radiation. Observations of relativistic particles place limits on the speed of gravitational radiation and the cosmological boundary values today, and observations of synchroton radiation from compact radio sources place limits on the cosmological boundary values in the past.

Preventing road injuries in children by applying feedback devices.

PubMed

Spiegel, Rainer; Farahmand, Parvis; Da Silva, Fábio Anciães; Claassen, Jens; Kalla, Roger

2012-01-01

The objective of this article is to determine how to prevent road injuries in schoolchildren by reducing the prevalence of speeding. On a busy road in the neighborhood of a preschool and two secondary schools in Oberhaching (greater Munich, Germany), a board was mounted next to the road (visible to the drivers as well as the pedestrians). The board consisted of a picture of a smiling child. Underneath the picture, an LED display read "Thank you!" in green blinking letters when the speed limit was adhered to and "Slowly!" in red blinking letters when speeding was detected. The main outcome assessment was the number of drivers adhering to the speed limit in the experimental condition (i.e., facing the device) compared to the number in the control condition (on the same road within the same time period but traveling in the opposite direction; i.e., drivers not facing the device). In the control condition 27.6 percent (230) of drivers adhered to the speed limit compared to 41.1 percent (427) of drivers in the experimental condition, χ(2) = 36.1, P < .0001. Only 12 drivers exceeded the speed limit by more than 20 km per hour in the experimental condition, whereas 34 drivers did so in the control condition, χ(2) = 9.6, P < .01. The display is associated with a significantly lower percentage of speeding drivers but does not seem to be sufficient, because the majority of drivers still did not observe the speed limit in the presence of the display. Additional factors on how speed reduction can be achieved will be discussed in the light of future applications and possible modifications of the device.

Stated response to increased enforcement density and penalty size for speeding and driving unbelted.

PubMed

Hössinger, Reinhard; Berger, Wolfgang J

2012-11-01

To what extent can traffic offences be reduced through stronger enforcement, higher penalties, and the provision of information to road users? This question was addressed with respect to the offences of "speeding" and "driving unbelted." Data were collected by a telephone survey of admitted speeders, followed by 438 face-to-face stated response interviews. Based on the data collected, separate statistical models were developed for the two offences. The models predict the behavioral effect of increasing enforcement density and/or penalty size as well as the additional effect of providing information to car drivers. All three factors are predicted to be effective in reducing speeding. According to the model, one additional enforcement event per year will cause a driver to reduce his current frequency of speeding by 5%. A penalty increase of 10 Euros is predicted to have the same effect. An announcement of stronger enforcement or higher fines is predicted to have an additional effect on behavior, independent of the actual magnitudes of increase in enforcement or fines. With respect to the use of a seat belt, however, neither an increase in enforcement density nor its announcement is predicted to have a significant effect on driver behavior. An increase in the penalty size is predicted to raise the stated wearing rate, which is already 90% in Austria. It seems that both the fear of punishment and the motivation for driving unbelted are limited, so that there is only a weak tradeoff between the two. This may apply to most traffic offences, with the exception of speeding, which accounts for over 80% of tickets alone, whereas all other offences account for less than 3% each. Copyright © 2012 Elsevier Ltd. All rights reserved.

Concurrent Flame Growth, Spread and Extinction over Composite Fabric Samples in Low Speed Purely Forced Flow in Microgravity

NASA Technical Reports Server (NTRS)

Zhao, Xiaoyang; T'ien, James S.; Ferkul, Paul V.; Olson, Sandra L.

2015-01-01

As a part of the NASA BASS and BASS-II experimental projects aboard the International Space Station, flame growth, spread and extinction over a composite cotton-fiberglass fabric blend (referred to as the SIBAL fabric) were studied in low-speed concurrent forced flows. The tests were conducted in a small flow duct within the Microgravity Science Glovebox. The fuel samples measured 1.2 and 2.2 cm wide and 10 cm long. Ambient oxygen was varied from 21% down to 16% and flow speed from 40 cm/s down to 1 cm/s. A small flame resulted at low flow, enabling us to observe the entire history of flame development including ignition, flame growth, steady spread (in some cases) and decay at the end of the sample. In addition, by decreasing flow velocity during some of the tests, low-speed flame quenching extinction limits were found as a function of oxygen percentage. The quenching speeds were found to be between 1 and 5 cm/s with higher speed in lower oxygen atmosphere. The shape of the quenching boundary supports the prediction by earlier theoretical models. These long duration microgravity experiments provide a rare opportunity for solid fuel combustion since microgravity time in ground-based facilities is generally not sufficient. This is the first time that a low-speed quenching boundary in concurrent spread is determined in a clean and unambiguous manner.

Ceramics for the advanced automotive gas turbine engine: A look at a single shaft design

NASA Technical Reports Server (NTRS)

Nosek, S. M.

1977-01-01

The results of a preliminary analysis of a single shaft regenerative design with a single stage radial turbine are presented to show the fuel economy that can be achieved at high turbine inlet temperatures, with this particular advanced design, if the turbine tip speed and regenerator inlet temperature are not limited. The engine size was 100 hp for application to a 3500 lb auto. The fuel economy was analyzed by coupling the engine to the auto through a continuously variable speed-ratio transmission and operating the system at constant turbine inlet temperature over the Composite Driving Cycle. The fuel was gasoline and the analysis was for a 85 F day. With a turbine inlet temperature of 2500 F the fuel economy was 26.2 mpg, an improvement of 18 percent over that of 22.3 mpg with a turbine inlet temperature of 1900 F. The turbine tip speed needed for best economy with the 2500 F engine was 2530 ft/sec. The regenerator temperature was approximately 2200 F at idle. Disk stresses were estimated for one single stage radial turbine and two two-stage radial-axial turbines and compared with maximum allowable stress curves estimated for a current ceramic material. Results show a need for higher Weibull Modulus, higher strength ceramics.

Local Limit Phenomena, Flow Compression, and Fuel Cracking Effects in High-Speed Turbulent Flames

DTIC Science & Technology

2015-06-01

e.g. local extinction and re- ignition , interactions between flow compression and fast-reaction induced dilatation (reaction compression ), and to...time as a function of initial temperature in constant-pressure auto - ignition , and (b) the S-curves of perfectly stirred reactors (PSRs), for n...mechanism. The reduction covered auto - ignition and perfectly stirred reactors for equivalence ratio range of 0.5~1.5, initial temperature higher than

The effect of three surface conditions, speed and running experience on vertical acceleration of the tibia during running.

PubMed

Boey, Hannelore; Aeles, Jeroen; Schütte, Kurt; Vanwanseele, Benedicte

2017-06-01

Research has focused on parameters that are associated with injury risk, e.g. vertical acceleration. These parameters can be influenced by running on different surfaces or at different running speeds, but the relationship between them is not completely clear. Understanding the relationship may result in training guidelines to reduce the injury risk. In this study, thirty-five participants with three different levels of running experience were recruited. Participants ran on three different surfaces (concrete, synthetic running track, and woodchip trail) at two different running speeds: a self-selected comfortable speed and a fixed speed of 3.06 m/s. Vertical acceleration of the lower leg was measured with an accelerometer. The vertical acceleration was significantly lower during running on the woodchip trail in comparison with the synthetic running track and the concrete, and significantly lower during running at lower speed in comparison with during running at higher speed on all surfaces. No significant differences in vertical acceleration were found between the three groups of runners at fixed speed. Higher self-selected speed due to higher performance level also did not result in higher vertical acceleration. These results may show that running on a woodchip trail and slowing down could reduce the injury risk at the tibia.

High-speed imaging using 3CCD camera and multi-color LED flashes

NASA Astrophysics Data System (ADS)

Hijazi, Ala; Friedl, Alexander; Cierpka, Christian; Kähler, Christian; Madhavan, Vis

2017-11-01

This paper demonstrates the possibility of capturing full-resolution, high-speed image sequences using a regular 3CCD color camera in conjunction with high-power light emitting diodes of three different colors. This is achieved using a novel approach, referred to as spectral-shuttering, where a high-speed image sequence is captured using short duration light pulses of different colors that are sent consecutively in very close succession. The work presented in this paper demonstrates the feasibility of configuring a high-speed camera system using low cost and readily available off-the-shelf components. This camera can be used for recording six-frame sequences at frame rates up to 20 kHz or three-frame sequences at even higher frame rates. Both color crosstalk and spatial matching between the different channels of the camera are found to be within acceptable limits. A small amount of magnification difference between the different channels is found and a simple calibration procedure for correcting the images is introduced. The images captured using the approach described here are of good quality to be used for obtaining full-field quantitative information using techniques such as digital image correlation and particle image velocimetry. A sequence of six high-speed images of a bubble splash recorded at 400 Hz is presented as a demonstration.

Traffic safety facts 1994 : speed

DOT National Transportation Integrated Search

1995-01-01

Speeding - exceeding the posted speed limit or driving too fast for conditions - is one of the most prevalent factors contributing to traffic crashes. In 1994, speed was a factor in 30 percent of all fatal crashes, and 12,480 lives were lost in speed...

Speed Variance and Its Influence on Accidents.

ERIC Educational Resources Information Center

Garber, Nicholas J.; Gadirau, Ravi

A study was conducted to investigate the traffic engineering factors that influence speed variance and to determine to what extent speed variance affects accident rates. Detailed analyses were carried out to relate speed variance with posted speed limit, design speeds, and other traffic variables. The major factor identified was the difference…

A health impact assessment of a proposed bill to decrease speed limits on local roads in Massachusetts (U.S.A.).

PubMed

James, Peter; Ito, Kate; Banay, Rachel F; Buonocore, Jonathan J; Wood, Benjamin; Arcaya, Mariana C

2014-10-02

Decreasing traffic speeds increases the amount of time drivers have to react to road hazards, potentially averting collisions, and makes crashes that do happen less severe. Boston's regional planning agency, the Metropolitan Area Planning Council (MAPC), in partnership with the Massachusetts Department of Public Health (MDPH), conducted a Health Impact Assessment (HIA) that examined the potential health impacts of a proposed bill in the state legislature to lower the default speed limits on local roads from 30 miles per hour (mph) to 25 mph. The aim was to reduce vehicle speeds on local roads to a limit that is safer for pedestrians, cyclists, and children. The passage of this proposed legislation could have had far-reaching and potentially important public health impacts. Lower default speed limits may prevent around 18 fatalities and 1200 serious injuries to motorists, cyclists and pedestrians each year, as well as promote active transportation by making local roads feel more hospitable to cyclists and pedestrians. While a lower speed limit would increase congestion and slightly worsen air quality, the benefits outweigh the costs from both a health and economic perspective and would save the state approximately $62 million annually from prevented fatalities and injuries.

A Health Impact Assessment of a Proposed Bill to Decrease Speed Limits on Local Roads in Massachusetts (U.S.A.)

PubMed Central

James, Peter; Ito, Kate; Banay, Rachel F.; Buonocore, Jonathan J.; Wood, Benjamin; Arcaya, Mariana C.

2014-01-01

Decreasing traffic speeds increases the amount of time drivers have to react to road hazards, potentially averting collisions, and makes crashes that do happen less severe. Boston’s regional planning agency, the Metropolitan Area Planning Council (MAPC), in partnership with the Massachusetts Department of Public Health (MDPH), conducted a Health Impact Assessment (HIA) that examined the potential health impacts of a proposed bill in the state legislature to lower the default speed limits on local roads from 30 miles per hour (mph) to 25 mph. The aim was to reduce vehicle speeds on local roads to a limit that is safer for pedestrians, cyclists, and children. The passage of this proposed legislation could have had far-reaching and potentially important public health impacts. Lower default speed limits may prevent around 18 fatalities and 1200 serious injuries to motorists, cyclists and pedestrians each year, as well as promote active transportation by making local roads feel more hospitable to cyclists and pedestrians. While a lower speed limit would increase congestion and slightly worsen air quality, the benefits outweigh the costs from both a health and economic perspective and would save the state approximately $62 million annually from prevented fatalities and injuries. PMID:25279544

Effects of Raising Speed Limits on Motor Vehicle Emissions

DOT National Transportation Integrated Search

1997-03-01

In 1974 the Federal government introduced a national speed limit of 55 miles per hour (mph) in response to the Arab oil embargo and subsequent energy crisis. This limit was raised to 65 mph for rural interstate freeways in 1987. In November of 1995, ...

THRUST BEARING

DOEpatents

Heller, P.R.

1958-09-16

A thrust bearing suitable for use with a rotor or blower that is to rotate about a vertical axis is descrihed. A centrifagal jack is provided so thnt the device may opernte on one hearing at starting and lower speeds, and transfer the load to another bearing at higher speeds. A low viscosity fluid is used to lubricate the higher speed operation bearing, in connection with broad hearing -surfaces, the ability to withstand great loads, and a relatively high friction loss, as contraated to the lower speed operatio;n bearing which will withstand only light thrust loads but is sufficiently frictionfree to avoid bearing seizure during slow speed or startup operation. An axially aligned shaft pin provides the bearing surface for low rotational speeds, but at higher speed, weights operating against spring tension withdraw nthe shaft pin into the bearing proper and the rotor shaft comes in contact with the large bearing surfaces.

First-order aerodynamic and aeroelastic behavior of a single-blade installation setup

NASA Astrophysics Data System (ADS)

Gaunaa, M.; Bergami, L.; Guntur, S.; Zahle, F.

2014-06-01

Limitations on the wind speed at which blade installation can be performed bears important financial consequences. The installation cost of a wind farm could be significantly reduced by increasing the wind speed at which blade mounting operations can be carried out. This work characterizes the first-order aerodynamic and aeroelastic behavior of a single blade installation system, where the blade is grabbed by a yoke, which is lifted by the crane and stabilized by two taglines. A simple engineering model is formulated to describe the aerodynamic forcing on the blade subject to turbulent wind of arbitrary direction. The model is coupled with a schematic aeroelastic representation of the taglines system, which returns the minimum line tension required to compensate for the aerodynamic forcing. The simplified models are in excellent agreement with the aeroelastic code HAWC2, and provide a solid basis for future design of an upgraded single blade installation system able to operate at higher wind speeds.

The Longitudinal Stability of Flying Boats as Determined by Tests of Models in the NACA Tank II : Effect of Variations in Form of Hull on Longitudinal Stability

NASA Technical Reports Server (NTRS)

Olson, Roland E.; Truscott, Starr

1942-01-01

Data taken from tests at constant speed to establish trim limits of stability, tests at accelerated speeds to determine stable limits of center of gravity shift, and tests at decelerated speeds to obtain landing characteristics of several model hull forms were used to establish hull design effect on longitudinal stability of porpoising. Results show a reduction of dead rise angle as being the only investigated factor reducing low trim limit. Various methods of reducing afterbody interference increased upper trim limit

Grip and limb force limits to turning performance in competition horses

PubMed Central

Tan, Huiling; Wilson, Alan M.

2011-01-01

Manoeuverability is a key requirement for successful terrestrial locomotion, especially on variable terrain, and is a deciding factor in predator–prey interaction. Compared with straight-line running, bend running requires additional leg force to generate centripetal acceleration. In humans, this results in a reduction in maximum speed during bend running and a published model assuming maximum limb force as a constraint accurately predicts how much a sprinter must slow down on a bend given his maximum straight-line speed. In contrast, greyhounds do not slow down or change stride parameters during bend running, which suggests that their limbs can apply the additional force for this manoeuvre. We collected horizontal speed and angular velocity of heading of horses while they turned in different scenarios during competitive polo and horse racing. The data were used to evaluate the limits of turning performance. During high-speed turns of large radius horizontal speed was lower on the bend, as would be predicted from a model assuming a limb force limit to running speed. During small radius turns the angular velocity of heading decreased with increasing speed in a manner consistent with the coefficient of friction of the hoof–surface interaction setting the limit to centripetal force to avoid slipping. PMID:21147799

Grip and limb force limits to turning performance in competition horses.

PubMed

Tan, Huiling; Wilson, Alan M

2011-07-22

Manoeuverability is a key requirement for successful terrestrial locomotion, especially on variable terrain, and is a deciding factor in predator-prey interaction. Compared with straight-line running, bend running requires additional leg force to generate centripetal acceleration. In humans, this results in a reduction in maximum speed during bend running and a published model assuming maximum limb force as a constraint accurately predicts how much a sprinter must slow down on a bend given his maximum straight-line speed. In contrast, greyhounds do not slow down or change stride parameters during bend running, which suggests that their limbs can apply the additional force for this manoeuvre. We collected horizontal speed and angular velocity of heading of horses while they turned in different scenarios during competitive polo and horse racing. The data were used to evaluate the limits of turning performance. During high-speed turns of large radius horizontal speed was lower on the bend, as would be predicted from a model assuming a limb force limit to running speed. During small radius turns the angular velocity of heading decreased with increasing speed in a manner consistent with the coefficient of friction of the hoof-surface interaction setting the limit to centripetal force to avoid slipping.

Optimal trajectories for an aerospace plane. Part 1: Formulation, results, and analysis

NASA Technical Reports Server (NTRS)

Miele, Angelo; Lee, W. Y.; Wu, G. D.

1990-01-01

The optimization of the trajectories of an aerospace plane is discussed. This is a hypervelocity vehicle capable of achieving orbital speed, while taking off horizontally. The vehicle is propelled by four types of engines: turbojet engines for flight at subsonic speeds/low supersonic speeds; ramjet engines for flight at moderate supersonic speeds/low hypersonic speeds; scramjet engines for flight at hypersonic speeds; and rocket engines for flight at near-orbital speeds. A single-stage-to-orbit (SSTO) configuration is considered, and the transition from low supersonic speeds to orbital speeds is studied under the following assumptions: the turbojet portion of the trajectory has been completed; the aerospace plane is controlled via the angle of attack and the power setting; the aerodynamic model is the generic hypersonic aerodynamics model example (GHAME). Concerning the engine model, three options are considered: (EM1), a ramjet/scramjet combination in which the scramjet specific impulse tends to a nearly-constant value at large Mach numbers; (EM2), a ramjet/scramjet combination in which the scramjet specific impulse decreases monotonically at large Mach numbers; and (EM3), a ramjet/scramjet/rocket combination in which, owing to stagnation temperature limitations, the scramjet operates only at M approx. less than 15; at higher Mach numbers, the scramjet is shut off and the aerospace plane is driven only by the rocket engines. Under the above assumptions, four optimization problems are solved using the sequential gradient-restoration algorithm for optimal control problems: (P1) minimization of the weight of fuel consumed; (P2) minimization of the peak dynamic pressure; (P3) minimization of the peak heating rate; and (P4) minimization of the peak tangential acceleration.

Examination of the wind speed limit function in the Rothermel surface fire spread model

Treesearch

Patricia L. Andrews; Miguel G. Cruz; Richard C. Rothermel

2013-01-01

The Rothermel surface fire spread model includes a wind speed limit, above which predicted rate of spread is constant. Complete derivation of the wind limit as a function of reaction intensity is given, along with an alternate result based on a changed assumption. Evidence indicates that both the original and the revised wind limits are too restrictive. Wind limit is...

Stokes waves revisited: Exact solutions in the asymptotic limit

NASA Astrophysics Data System (ADS)

Davies, Megan; Chattopadhyay, Amit K.

2016-03-01

The Stokes perturbative solution of the nonlinear (boundary value dependent) surface gravity wave problem is known to provide results of reasonable accuracy to engineers in estimating the phase speed and amplitudes of such nonlinear waves. The weakling in this structure though is the presence of aperiodic "secular variation" in the solution that does not agree with the known periodic propagation of surface waves. This has historically necessitated increasingly higher-ordered (perturbative) approximations in the representation of the velocity profile. The present article ameliorates this long-standing theoretical insufficiency by invoking a compact exact n -ordered solution in the asymptotic infinite depth limit, primarily based on a representation structured around the third-ordered perturbative solution, that leads to a seamless extension to higher-order (e.g., fifth-order) forms existing in the literature. The result from this study is expected to improve phenomenological engineering estimates, now that any desired higher-ordered expansion may be compacted within the same representation, but without any aperiodicity in the spectral pattern of the wave guides.

14 CFR 27.1521 - Powerplant limitations.

Code of Federal Regulations, 2010 CFR

2010-01-01

...) The gas temperature limits for turbine engines over the range of operating and atmospheric conditions... rotational speed shown under the rotor speed requirements in § 27.1509(c); and (3) The gas temperature limits for turbine engines over the range of operating and atmospheric conditions for which certification is...

14 CFR 27.1521 - Powerplant limitations.

Code of Federal Regulations, 2013 CFR

2013-01-01

...) The gas temperature limits for turbine engines over the range of operating and atmospheric conditions... rotational speed shown under the rotor speed requirements in § 27.1509(c); and (3) The gas temperature limits for turbine engines over the range of operating and atmospheric conditions for which certification is...

14 CFR 27.1521 - Powerplant limitations.

Code of Federal Regulations, 2011 CFR

2011-01-01

...) The gas temperature limits for turbine engines over the range of operating and atmospheric conditions... rotational speed shown under the rotor speed requirements in § 27.1509(c); and (3) The gas temperature limits for turbine engines over the range of operating and atmospheric conditions for which certification is...

14 CFR 27.1521 - Powerplant limitations.

Code of Federal Regulations, 2012 CFR

2012-01-01

...) The gas temperature limits for turbine engines over the range of operating and atmospheric conditions... rotational speed shown under the rotor speed requirements in § 27.1509(c); and (3) The gas temperature limits for turbine engines over the range of operating and atmospheric conditions for which certification is...

14 CFR 27.1521 - Powerplant limitations.

Code of Federal Regulations, 2014 CFR

2014-01-01

...) The gas temperature limits for turbine engines over the range of operating and atmospheric conditions... rotational speed shown under the rotor speed requirements in § 27.1509(c); and (3) The gas temperature limits for turbine engines over the range of operating and atmospheric conditions for which certification is...

Minor methane emissions from an Alpine hydropower reservoir based on monitoring of diel and seasonal variability.

PubMed

Sollberger, Sébastien; Wehrli, Bernhard; Schubert, Carsten J; DelSontro, Tonya; Eugster, Werner

2017-10-18

We monitored CH 4 emissions during the ice-free period of an Alpine hydropower reservoir in the Swiss Alps, Lake Klöntal, to investigate mechanisms responsible for CH 4 variability and to estimate overall emissions to the atmosphere. A floating eddy-covariance platform yielded total CH 4 and CO 2 emission rates at high temporal resolution, while hydroacoustic surveys provided no indication of CH 4 ebullition. Higher CH 4 fluxes (2.9 ± 0.1 mg CH 4 per m 2 per day) occurred during the day when surface water temperatures were warmer and wind speeds higher than at night. Piston velocity estimates (k 600 ) showed an upper limit at high wind speeds that may be more generally valid also for other lakes and reservoirs with limited CH 4 dissolved in the water body: above 2.0 m s -1 a further increase in wind speed did not lead to higher CH 4 fluxes, because under such conditions it is not the turbulent mixing and transport that limits effluxes, but the resupply of CH 4 to the lake surface. Increasing CH 4 fluxes during the warm season showed a clear spatial gradient once the reservoir started to fill up and flood additional surface area. The warm period contributed 27% of the total CH 4 emissions (2.6 t CH 4 per year) estimated for the full year and CH 4 accounted for 63% of carbonic greenhouse gas emissions. Overall, the average CH 4 emissions (1.7 to 2.2 mg CH 4 per m 2 per day determined independently from surface water samplings and eddy covariance, respectively) were small compared to most tropical and some temperate reservoirs. The resulting greenhouse gas (GHG) emissions in CO 2 -equivalents revealed that electricity produced in the Lake Klöntal power plant was relatively climate-friendly with a low GHG-to-power output ratio of 1.24 kg CO 2,eq per MW h compared to 6.5 and 8.1 kg CO 2,eq per MW h associated with the operation of solar photovoltaics and wind energy, respectively, or about 980 kg CO 2,eq per MW h for coal-fired power plants.

Traffic safety facts 1998 : speeding

DOT National Transportation Integrated Search

1998-01-01

Speeding exceeding the posted speed limit or driving too fast for : The economic cost : of speeding-related : crashes is estimated : to be $27.7 billion : each year. : conditions is one of the most prevalent factors contributing to traf...

Speeds in school zones.

DOT National Transportation Integrated Search

2009-02-01

School speed zones are frequently requested traffic controls for school areas, based on the common belief : that if the transportation agency would only install a reduced speed limit, then drivers would no longer : speed through the area. This resear...

Quantitative Measurement of Vocal Fold Vibration in Male Radio Performers and Healthy Controls Using High-Speed Videoendoscopy

PubMed Central

Warhurst, Samantha; McCabe, Patricia; Heard, Rob; Yiu, Edwin; Wang, Gaowu; Madill, Catherine

2014-01-01

Purpose Acoustic and perceptual studies show a number of differences between the voices of radio performers and controls. Despite this, the vocal fold kinematics underlying these differences are largely unknown. Using high-speed videoendoscopy, this study sought to determine whether the vocal vibration features of radio performers differed from those of non-performing controls. Method Using high-speed videoendoscopy, recordings of a mid-phonatory/i/ in 16 male radio performers (aged 25–52 years) and 16 age-matched controls (aged 25–52 years) were collected. Videos were extracted and analysed semi-automatically using High-Speed Video Program, obtaining measures of fundamental frequency (f0), open quotient and speed quotient. Post-hoc analyses of sound pressure level (SPL) were also performed (n = 19). Pearson's correlations were calculated between SPL and both speed and open quotients. Results Male radio performers had a significantly higher speed quotient than their matched controls (t = 3.308, p = 0.005). No significant differences were found for f0 or open quotient. No significant correlation was found between either open or speed quotient with SPL. Discussion A higher speed quotient in male radio performers suggests that their vocal fold vibration was characterised by a higher ratio of glottal opening to closing times than controls. This result may explain findings of better voice quality, higher equivalent sound level and greater spectral tilt seen in previous research. Open quotient was not significantly different between groups, indicating that the durations of complete vocal fold closure were not different between the radio performers and controls. Further validation of these results is required to determine the aetiology of the higher speed quotient result and its implications for voice training and clinical management in performers. PMID:24971625

Reliability analysis of degradable networks with modified BPR

NASA Astrophysics Data System (ADS)

Wang, Yu-Qing; Zhou, Chao-Fan; Jia, Bin; Zhu, Hua-Bing

2017-12-01

In this paper, the effect of the speed limit on degradable networks with capacity restrictions and the forced flow is investigated. The link performance function considering the road capacity is proposed. Additionally, the probability density distribution and the cumulative distribution of link travel time are introduced in the degradable network. By the mean of distinguishing the value of the speed limit, four cases are discussed, respectively. Means and variances of link travel time and route one of the degradable road network are calculated. Besides, by the mean of performing numerical simulation experiments in a specific network, it is found that the speed limit strategy can reduce the travel time budget and mean travel time of link and route. Moreover, it reveals that the speed limit strategy can cut down variances of the travel time of networks to some extent.

Design of voice coil motor dynamic focusing unit for a laser scanner

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

Lee, Moon G.; Kim, Gaeun; Lee, Chan-Woo

2014-04-15

Laser scanning systems have been used for material processing tasks such as welding, cutting, marking, and drilling. However, applications have been limited by the small range of motion and slow speed of the focusing unit, which carries the focusing optics. To overcome these limitations, a dynamic focusing system with a long travel range and high speed is needed. In this study, a dynamic focusing unit for a laser scanning system with a voice coil motor (VCM) mechanism is proposed to enable fast speed and a wide focusing range. The VCM has finer precision and higher speed than conventional step motorsmore » and a longer travel range than earlier lead zirconium titanate actuators. The system has a hollow configuration to provide a laser beam path. This also makes it compact and transmission-free and gives it low inertia. The VCM's magnetics are modeled using a permeance model. Its design parameters are determined by optimization using the Broyden–Fletcher–Goldfarb–Shanno method and a sequential quadratic programming algorithm. After the VCM is designed, the dynamic focusing unit is fabricated and assembled. The permeance model is verified by a magnetic finite element method simulation tool, Maxwell 2D and 3D, and by measurement data from a gauss meter. The performance is verified experimentally. The results show a resolution of 0.2 μm and travel range of 16 mm. These are better than those of conventional focusing systems; therefore, this focusing unit can be applied to laser scanning systems for good machining capability.« less

The mediating role of C-reactive protein and handgrip strength between obesity and walking limitation.

PubMed

Stenholm, Sari; Rantanen, Taina; Heliövaara, Markku; Koskinen, Seppo

2008-03-01

To study the association between different obesity indicators and walking limitation and to examine the role of C-reactive protein (CRP) and handgrip strength in that association. A cross-sectional, population-based study. The Health 2000 Survey with a representative sample of the Finnish population. Subjects aged 55 and older with complete data on body composition, CRP, handgrip strength, and walking limitation (N=2,208). Body composition, anthropometrics, CRP, medical conditions, handgrip strength, and maximal walking speed were measured in the health examination. Walking limitation was defined as maximal walking speed less than 1.2 m/s or difficulty walking half a kilometer. The two highest quartiles of body fat percentage and CRP and the two lowest quartiles of handgrip strength were all significantly associated with greater risk of walking limitation when chronic diseases and other covariates were taken into account. In addition, high CRP and low handgrip strength partially explained the association between high body fat percentage and walking limitation, but the risk of walking limitation remained significantly greater in persons in the two highest quartiles than in those in the lowest quartile of body fat percentage (odds ratio (OR)=1.75, 95% confidence interval (CI)=1.19-2.57 and OR=2.80, 95% CI 1.89-4.16). The prevalence of walking limitation was much higher in persons who simultaneously had high body fat percentage and low handgrip strength (61%) than in those with a combination of low body fat percentage and high handgrip strength (7%). Using body mass index and waist circumference as indicators of obesity yielded similar results as body fat percentage. Low-grade inflammation and muscle strength may partially mediate the association between obesity and walking limitation. Longitudinal studies and intervention trials are needed to verify this pathway.

Programmable logic controller performance enhancement by field programmable gate array based design.

PubMed

Patel, Dhruv; Bhatt, Jignesh; Trivedi, Sanjay

2015-01-01

PLC, the core element of modern automation systems, due to serial execution, exhibits limitations like slow speed and poor scan time. Improved PLC design using FPGA has been proposed based on parallel execution mechanism for enhancement of performance and flexibility. Modelsim as simulation platform and VHDL used to translate, integrate and implement the logic circuit in FPGA. Xilinx's Spartan kit for implementation-testing and VB has been used for GUI development. Salient merits of the design include cost-effectiveness, miniaturization, user-friendliness, simplicity, along with lower power consumption, smaller scan time and higher speed. Various functionalities and applications like typical PLC and industrial alarm annunciator have been developed and successfully tested. Results of simulation, design and implementation have been reported. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

Effects of ionic liquids on the performance of IPMC

NASA Astrophysics Data System (ADS)

Kim, Min Jung; Park, Sang Woo; Won, Joohye; Nah, Changwoon

2017-04-01

One of the issues in operating the IPMC actuators in air condition is the limited lifetime due to the evaporation of aqueous electrolytes like water. Several attempts were already made for solving the problem using an ionic liquid (IL) with higher boiling point. In this study, three different ILs having similar boiling point but different molecular weight were employed in the IPMC actuators. The actuation performance, notably speed and lifetime, were measured and they are compared with that of water-based IPMC actuator. The lower molecular weight IL showed a comparable actuation speed of water due to faster movement of the ion cluster. The lifetime of the water-based IPMC actuator was found to be only 3 hr. However, the IL-based IPMC actuators showed much improved service life.

Advanced radial inflow turbine rotor program: Design and dynamic testing

NASA Technical Reports Server (NTRS)

Rodgers, C.

1976-01-01

The advancement of small, cooled, radial inflow turbine technology in the area of operation at higher turbine inlet temperature is discussed. The first step was accomplished by designing, fabricating, and subjecting to limited mechanical testing an advanced gas generator rotating assembly comprising a radial inflow turbine and two-stage centrifugal compressor. The radial inflow turbine and second-stage compressor were designed as an integrally machined monorotor with turbine cooling taking place basically by conduction to the compressor. Design turbine inlet rotor gas temperature, rotational speed, and overall gas generator compressor pressure ratio were 1422 K (2560 R), 71,222 rpm, and 10/1 respectively. Mechanical testing on a fabricated rotating assembly and bearing system covered 1,000 cold start/stop cycles and three spins to 120 percent design speed (85,466 rpm).

Non-linear vehicle-bridge-wind interaction model for running safety assessment of high-speed trains over a high-pier viaduct

NASA Astrophysics Data System (ADS)

Olmos, José M.; Astiz, Miguel Á.

2018-04-01

In order to properly study the high-speed traffic safety on a high-pier viaduct subject to episodes of lateral turbulent winds, an efficient dynamic interaction train-bridge-wind model has been developed and experimentally validated. This model considers the full wheel and rail profiles, the friction between these two bodies in contact, and the piers P-Delta effect. The model has been used to determine the critical train and wind velocities from which the trains cannot travel safely over the O'Eixo Bridge. The dynamic simulations carried out and the results obtained in the time domain show that traffic safety rates exceed the allowed limits for turbulent winds with mean velocities at the deck higher than 25 m/s.

Control system to reduce the effects of friction in drive trains of continuous-path-positioning systems. [Patent application

DOEpatents

Green, W.L.

1980-12-01

An improved continuous-path-positioning servo-control system is provided for reducing the effects of friction arising at very low cutting speeds in the drive trains of numerically controlled cutting machines, and the like. The improvement comprises a feed forward network for altering the gain of the servo-control loop at low positioning velocities to prevent stick-slip movement of the cutting tool holder being positioned by the control system. The feed forward network shunts conventional lag-compensators in the control loop, or loops, so that the error signal used for positioning varies linearly when the value is small, but being limited for larger values. Thus, at higher positioning speeds there is little effect of the added component upon the control being achieved.

Triple flames and flame stabilization

NASA Technical Reports Server (NTRS)

Broadwell, James E.

1994-01-01

It is now well established that when turbulent jet flames are lifted, combustion begins, i.e., the flame is stabilized, at an axial station where the fuel and air are partially premixed. One might expect, therefore, that the beginning of the combustion zone would be a triple flame. Such flames have been described; however, other experiments provide data that are difficult to reconcile with the presence of triple flames. In particular, laser images of CH and OH, marking combustion zones, do not exhibit shapes typical of triple flames, and, more significantly, the lifted flame appears to have a propagation speed that is an order of magnitude higher than the laminar flame speed. The speed of triple flames studied thus far exceeds the laminar value by a factor less than two. The objective of the present task is the resolution of the apparent conflict between the experiments and the triple flame characteristics, and the clarification of the mechanisms controlling flame stability. Being investigated are the resolution achieved in the experiments, the flow field in the neighborhood of the stabilization point, propagation speeds of triple flames, laboratory flame unsteadiness, and the importance of flame ignition limits in the calculation of triple flames that resemble lifted flames.

Ship collision risk assessment for the Singapore Strait.

PubMed

Qu, Xiaobo; Meng, Qiang; Suyi, Li

2011-11-01

The Singapore Strait is considered as the bottleneck and chokepoint of the shipping routes connecting the Indian and the Pacific Ocean. Therefore, the ship collision risk assessment is of significant importance for ships passing through the narrow, shallow, and busy waterway. In this paper, three ship collision risk indices are initially proposed to quantitatively assess the ship collision risks in the Strait: index of speed dispersion, degree of acceleration and deceleration, and number of fuzzy ship domain overlaps. These three risk indices for the Singapore Strait are estimated by using the real-time ship locations and sailing speeds provide by Lloyd's MIU automatic identification system (AIS). Based on estimation of these three risk indices, it can be concluded that Legs 4W, 5W, 11E, and 12E are the most risky legs in the Strait. Therefore, the ship collision risk reduction solutions should be prioritized being implemented in these four legs. This study also finds that around 25% of the vessels sail with a speed in excess of the speed limit, which results in higher potentials of ship collision. Analysis indicates that the safety level would be significantly improved if all the vessels follow the passage guidelines. Copyright © 2011 Elsevier Ltd. All rights reserved.

Transverse mixing of ellipsoidal particles in a rotating drum

NASA Astrophysics Data System (ADS)

He, Siyuan; Gan, Jieqing; Pinson, David; Zhou, Zongyan

2017-06-01

Rotating drums are widely used in industry for mixing, milling, coating and drying processes. In the past decades, mixing of granular materials in rotating drums has been extensively investigated, but most of the studies are based on spherical particles. Particle shape has an influence on the flow behaviour and thus mixing behaviour, though the shape effect has as-yet received limited study. In this work, discrete element method (DEM) is employed to study the transverse mixing of ellipsoidal particles in a rotating drum. The effects of aspect ratio and rotating speed on mixing quality and mixing rate are investigated. The results show that mixing index increases exponentially with time for both spheres and ellipsoids. Particles with various aspect ratios are able to reach well-mixed states after sufficient revolutions in the rolling or cascading regime. Ellipsoids show higher mixing rate when rotational speed is set between 25 and 40 rpm. The relationship between mixing rate and aspect ratio of ellipsoids is established, demonstrating that, particles with aspect ratios of 0.5 and 2.0 achieve the highest mixing rates. Increasing rotating speed from 15 rpm to 40 rpm does not necessarily increase the mixing speed of spheres, while monotonous increase is observed for ellipsoids.

A methodology for achieving high-speed rates for artificial conductance injection in electrically excitable biological cells.

PubMed

Butera, R J; Wilson, C G; Delnegro, C A; Smith, J C

2001-12-01

We present a novel approach to implementing the dynamic-clamp protocol (Sharp et al., 1993), commonly used in neurophysiology and cardiac electrophysiology experiments. Our approach is based on real-time extensions to the Linux operating system. Conventional PC-based approaches have typically utilized single-cycle computational rates of 10 kHz or slower. In thispaper, we demonstrate reliable cycle-to-cycle rates as fast as 50 kHz. Our system, which we call model reference current injection (MRCI); pronounced merci is also capable of episodic logging of internal state variables and interactive manipulation of model parameters. The limiting factor in achieving high speeds was not processor speed or model complexity, but cycle jitter inherent in the CPU/motherboard performance. We demonstrate these high speeds and flexibility with two examples: 1) adding action-potential ionic currents to a mammalian neuron under whole-cell patch-clamp and 2) altering a cell's intrinsic dynamics via MRCI while simultaneously coupling it via artificial synapses to an internal computational model cell. These higher rates greatly extend the applicability of this technique to the study of fast electrophysiological currents such fast a currents and fast excitatory/inhibitory synapses.

Examples of variable speed limit applications : speed management workshop

DOT National Transportation Integrated Search

2000-01-09

VSL systems are a type of Intelligent Transportation System (ITS) that utilizes traffic : speed and volume detection, weather information, and road surface condition technology to determine appropriate speeds at which drivers should be traveling, giv...

Gait Speed rather than Dynapenia Is a Simple Indicator for Complex Care Needs: A Cross-sectional Study Using Minimum Data Set.

PubMed

Huang, Tzu-Ya; Liang, Chih-Kuang; Shen, Hsiu-Chu; Chen, Hon-I; Liao, Mei-Chen; Chou, Ming-Yueh; Lin, Yu-Te; Chen, Liang-Kung

2017-08-21

The impact of dynapenia on the complexity of care for residents of long-term care facilities (LTCF) remains unclear. The present study evaluated associations between dynapenia, care problems and care complexity in 504 residents of Veterans Care Homes (VCHs) in Taiwan. Subjects with dynapenia, defined as low muscle strength (handgrip strength <26 kg), were older adults with lower body mass index (BMI), slow gait speed, and higher numbers of Resident Assessment Protocol (RAP) triggers. After adjusting for age, education, BMI, and Charlson's comorbidity index (CCI), only age, education, BMI and gait speed were independently associated with higher numbers of RAP triggers, but not dynapenia or handgrip strength (kg). Dividing subjects into groups based on quartiles of gait speed, those with gait speed ≤0.803 m/s were significantly associated with higher complexity of care needs (defined as ≥4 RAP triggers) compared to the reference group (gait speed >1 m/s). Significantly slow gait speed was associated with RAP triggers, including cognitive loss, poor communication ability, rehabilitation needs, urinary incontinence, depressed mood, falls, pressure ulcers, and use of psychotropic drugs. In conclusion, slow gait speed rather than dynapenia is a simple indicator for higher complexity of care needs of older male LTCF residents.

Physical Performance and Serum 25(OH)vitamin D Status in Community Dwelling Old Mobility Limited Adults: A Cross-Sectional Study.

PubMed

von Berens, Å; Cederholm, T; Fielding, R A; Gustafsson, T; Kirn, D; Laussen, J; Nydahl, M; Travison, T G; Reid, K; Koochek, A

2018-01-01

To examine the potential association between serum 25(OH) vitamin D and the performance on the Short Physical Performance Battery (SPPB) including the sub-components; five repeated chair stands test, 4 meters walk test and balance in older mobility-limited community-dwelling men and women. A cross sectional study was performed in American and Swedish subjects who were examined for potential participation in a combined exercise and nutrition intervention trial. Logistic regression analysis and linear regression analyses were performed to evaluate the association for 25(OH)D with the overall score on the SBBP, chair stand, gait speed and balance. Community-dwelling (mean age 77.6 ± 5.3 years) mobility limited American (n=494) and Swedish (n=116) females (59%) and males. The SPPB (0-12 points) includes chair stand (s), gait speed (m/s) and a balance test. Mobility limitation i.e., SPPB score ≤ 9 was an inclusion criterion. A blood sample was obtained to measure serum 25(OH)vitamin D concentrations. No clear association of 25(OH)D with SPPB scores was detected either when 25(OH)D was assessed as a continuous variable or when categorized according to serum concentrations of <50, 50-75 or <75 nmol/L. However, when analyzing the relationship between 25(OH)D and seconds to perform the chair stands, a significant quadratic relationship was observed. Thus, at serum levels of 25(OH)D above 74 nmol/L, higher concentrations appeared to be advantageous for the chair stand test, whereas for serum levels below 74 nmol/L this association was not observed. This cross- sectional study lacked clear association between serum 25(OH)D and physical performance in mobility limited adults. A potentially interesting observation was that at higher serum levels of 25(OH)D a better performance on the chair stand test was indicated.

Intelligent advisory speed limit dedication in highway using VANET.

PubMed

Jalooli, Ali; Shaghaghi, Erfan; Jabbarpour, Mohammad Reza; Noor, Rafidah Md; Yeo, Hwasoo; Jung, Jason J

2014-01-01

Variable speed limits (VSLs) as a mean for enhancing road traffic safety are studied for decades to modify the speed limit based on the prevailing road circumstances. In this study the pros and cons of VSL systems and their effects on traffic controlling efficiency are summarized. Despite the potential effectiveness of utilizing VSLs, we have witnessed that the effectiveness of this system is impacted by factors such as VSL control strategy used and the level of driver compliance. Hence, the proposed approach called Intelligent Advisory Speed Limit Dedication (IASLD) as the novel VSL control strategy which considers the driver compliance aims to improve the traffic flow and occupancy of vehicles in addition to amelioration of vehicle's travel times. The IASLD provides the advisory speed limit for each vehicle exclusively based on the vehicle's characteristics including the vehicle type, size, and safety capabilities as well as traffic and weather conditions. The proposed approach takes advantage of vehicular ad hoc network (VANET) to accelerate its performance, in the way that simulation results demonstrate the reduction of incident detection time up to 31.2% in comparison with traditional VSL strategy. The simulation results similarly indicate the improvement of traffic flow efficiency, occupancy, and travel time in different conditions.

Match-to-match variation in physical activity and technical skill measures in professional Australian Football.

PubMed

Kempton, Thomas; Sullivan, Courtney; Bilsborough, Johann C; Cordy, Justin; Coutts, Aaron J

2015-01-01

To determine the match-to-match variability in physical activity and technical performance measures in Australian Football, and examine the influence of playing position, time of season, and different seasons on these measures of variability. Longitudinal observational study. Global positioning system, accelerometer and technical performance measures (total kicks, handballs, possessions and Champion Data rank) were collected from 33 players competing in the Australian Football League over 31 matches during 2011-2012 (N=511 observations). The global positioning system data were categorised into total distance, mean speed (mmin(-1)), high-speed running (>14.4 kmh(-1)), very high-speed running (>19.9 kmh(-1)), and sprint (>23.0 kmh(-1)) distance while player load was collected from the accelerometer. The data were log transformed to provide coefficient of variation and the between subject standard deviation (expressed as percentages). Match-to-match variability was increased for higher speed activities (high-speed running, very high-speed running, sprint distance, coefficient of variation %: 13.3-28.6%) compared to global measures (speed, total distance, player load, coefficient of variation %: 5.3-9.2%). The between-match variability was relativity stable for all measures between and within AFL seasons, with only few differences between positions. Higher speed activities (high-speed running, very high-speed running, sprint distance), but excluding mean speed, total distance and player load, were all higher in the final third phase of the season compared to the start of the season. While global measures of physical performance are relatively stable, higher-speed activities and technical measures exhibit a large degree of between-match variability in Australian Football. However, these measures remain relatively stable between positions, and within and between Australian Football League seasons. Copyright © 2013 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Limiting critical speed response on the SSME Alternate High Pressure Fuel Turbopump (ATD HPFTP) with bearing deadband

NASA Technical Reports Server (NTRS)

Goggin, David G.; Darden, J. M.

1992-01-01

Yammamoto (1954) described the influence of bearing deadband on the critical speed response of a rotor-bearing system. Practical application of these concepts to limit critical speed response of turbopump rotors is described. Nonlinear rotordynamic analyses are used to define the effect of bearing deadband and rotor unbalance on the Space Shuttle Main Engine Alternate High Pressure Fuel Turbopump. Analysis results are used with hot fire test data to verify the presence of a lightly damped critical speed within the operating speed range. With the proper control of rotor unbalance and bearing deadband, the response of this critical speed is reduced to acceptable levels without major design modifications or additional sources of damping.

The influence of curbs on driver behaviors in four-lane rural highways--A driving simulator based study.

PubMed

Yang, Qiang; Overton, Ryan; Han, Lee D; Yan, Xuedong; Richards, Stephen H

2013-01-01

The speed limit of 55mph (88km/h) is typically used on rural highways in the U.S. For locations where curbs are installed along these roadways, some transportation agencies have suggested the use of a lower 45mph (72km/h) speed limit because, according to AASHTO, running into curbs at high speeds may cause significant vehicular damage and even severe injuries. However, it has also been argued that lowering the speed limit after the installation of curbs may cause confusion in drivers, who do not perceive the risk associated with the newly installed curbs and tend to operate their vehicles at the same speed as before. To better understand driver behavior on rural highways before and after curb installation, and with different speed limits, researchers at the University of Tennessee conducted a series of experiments in two-lane and four-lane highways on a high-fidelity driving simulator. This paper mainly presents the findings from the four-lane study, and compares the results from the previous two-lane study. The scenario matrix consists of several dimensions including posted speed limit (45 and 55mph, or 72 and 88km/h), curb installation, lateral clearance between the edge of travel lane and the curb (2ft, 6ft, and no-curb, or 0.6m, 1.8m, and no-curb), weather (clear and fog), traffic conditions in the next lane (1400veh/h and 400veh/h), etc. For each subject under different experimental scenarios, detailed driving parameters, such as driving speed and vehicle position in the travel lane, were recorded and analyzed subsequently. Results of the study suggest that driver behaviors are influenced by the various factors in a complex and interrelated manner. It is likely that drivers do not perceive the risk from the curb in determining their speed on four-lane rural highways. However, it is found that curbs may provide certain guidance to drivers, especially in selecting lane position. Compared to the previous research in two-lane conditions, it is found that drivers are more likely to choose driving speeds according to posted speed limits, rather than lane configurations. It is also found that the relative speed between driver's vehicle and ambient traffic or curbs is an important factor determining drivers' perception of risk and thus their driving behavior. The influence of subjective effects of these factors to their driving behavior is also observed in the study. Copyright © 2012 Elsevier Ltd. All rights reserved.

Traffic safety facts 1995 : speeding

DOT National Transportation Integrated Search

1996-01-01

Speeding - exceeding the posted speed limit or driving too fast for conditions - is one of the most prevalent factors contributing to traffic crashes. In 1995, speeding was a contributing factor in 31 percent of all fatal crashes, and 13,256 lives we...

Traffic safety facts 1996 : speeding

DOT National Transportation Integrated Search

1997-01-01

Speeding - exceeding the posted speed limit or driving too fast for conditions - is one of the most prevalent factors contributing to traffic crashes. In 1996, speeding was a contributing factor in 30 percent of all fatal crashes, and 12,998 lives we...

Traffic safety facts 1999 : speeding

DOT National Transportation Integrated Search

2000-01-01

Speeding -- exceeding the posted speed limit or driving too fast for conditions -- is one of the most prevalent factors contributing to traffic crashes. In 1999, speeding was a contributing factor in 30% of all fatal crashes, and 12,628 lives were lo...

The effects of on-street parking and road environment visual complexity on travel speed and reaction time.

PubMed

Edquist, Jessica; Rudin-Brown, Christina M; Lenné, Michael G

2012-03-01

On-street parking is associated with elevated crash risk. It is not known how drivers' mental workload and behaviour in the presence of on-street parking contributes to, or fails to reduce, this increased crash risk. On-street parking tends to co-exist with visually complex streetscapes that may affect workload and crash risk in their own right. The present paper reports results from a driving simulator study examining the effects of on-street parking and road environment visual complexity on driver behaviour and surrogate measures of crash risk. Twenty-nine participants drove a simulated urban commercial and arterial route. Compared to sections with no parking bays or empty parking bays, in the presence of occupied parking bays drivers lowered their speed and shifted their lateral position towards roadway centre to compensate for the higher mental workload they reported experiencing. However, this compensation was not sufficient to reduce drivers' reaction time on a safety-relevant peripheral detection task or to an unexpected pedestrian hazard. Compared to the urban road environments, the less visually complex arterial road environment was associated with speeds that were closer to the posted limit, lower speed variability and lower workload ratings. These results support theoretical positions that proffer workload as a mediating variable of speed choice. However, drivers in this study did not modify their speed sufficiently to maintain safe hazard response times in complex environments with on-street parking. This inadequate speed compensation is likely to affect real world crash risk. Copyright © 2011 Elsevier Ltd. All rights reserved.

Reducing air-pollution: a new argument for getting drivers to abide by the speed limit?

PubMed

Delhomme, P; Chappé, J; Grenier, K; Pinto, M; Martha, C

2010-01-01

Speeding is one of the main factors of car crash-risk, but it also contributes to increasing air-pollution. In two studies we attempted to lead drivers to abide by speed limits using "reducing air-pollution" as a new argument. We presented prevention messages that highlighted the role of speeding in increasing "crash-risk", "air-pollution", or both (Studies 1 and 2). The messages were also positively or negatively framed (Study 2). Given that women are more concerned with environmental issues than are men, we expected the following hypotheses to be validated for women. The message with the "air-pollution" argument was expected to be evaluated more positively than the "crash-risk" message (H1). The "air-pollution" and "crash-risk and air-pollution" messages were expected to be more effective than the "crash-risk" message on the behavioral intention to observe speed limits (H2a) and on the perceived efficacy of speed-limit observance in reducing air-pollution (H2b; Studies 1 and 2). Furthermore, positive framing was expected to be more effective than negative framing (H3), and presenting a message to be more effective than presenting no message (H4; Study 2). Broadly, our results argue in favor of our hypotheses. However in Study 2, the effects of message framing did not allow us to conclude that negative or positive framing was superior. All in all, messages with the "air-pollution" argument were more effective at leading drivers to observe speed limits. Thus, environmental protection may be a fruitful route to explore for increasing road safety.

An Examination of Brain Abnormalities and Mobility in Individuals with Mild Cognitive Impairment and Alzheimer's Disease

PubMed Central

Fischer, Barbara L.; Bacher, Rhonda; Bendlin, Barbara B.; Birdsill, Alex C.; Ly, Martina; Hoscheidt, Siobhan M.; Chappell, Richard J.; Mahoney, Jane E.; Gleason, Carey E.

2017-01-01

Background: Mobility changes are concerning for elderly patients with cognitive decline. Given frail older individuals' vulnerability to injury, it is critical to identify contributors to limited mobility. Objective: To examine whether structural brain abnormalities, including reduced gray matter volume and white matter hyperintensities, would be associated with limited mobility among individuals with cognitive impairment, and to determine whether cognitive impairment would mediate this relationship. Methods: Thirty-four elderly individuals with mild cognitive impairment (MCI) and Alzheimer's disease underwent neuropsychological evaluation, mobility assessment, and structural brain neuroimaging. Linear regression was conducted with predictors including gray matter volume in six regions of interest (ROI) and white matter hyperintensity (WMH) burden, with mobility measures as outcomes. Results: Lower gray matter volume in caudate nucleus was associated with slower speed on a functional mobility task. Higher cerebellar volume was also associated with slower functional mobility. White matter hyperintensity burden was not significantly associated with mobility. Conclusion: Our findings provide evidence for associations between subcortical gray matter volume and speed on a functional mobility task among cognitively impaired individuals. PMID:28424612

Detection and quantification of cocaine and benzoylecgonine in meconium using solid phase extraction and UPLC/MS/MS.

PubMed

Gunn, Josh; Kriger, Scott; Terrell, Andrea R

2010-01-01

The simultaneous determination and quantification of cocaine and its major metabolite, benzoylecgonine, in meconium using UPLC-MS/MS is described. Ultra-performance liquid chromatography (UPLC) is an emerging analytical technique which draws upon the principles of chromatography to run separations at higher flow rates for increased speed, while simultaneously achieving superior resolution and sensitivity. Extraction of cocaine and benzoylecgonine from the homogenized meconium matrix was achieved with a preliminary protein precipitation or protein 'crash' employing cold acetonitrile, followed by a mixed mode solid phase extraction (SPE). Following elution from the SPE cartridge, eluents were dried down under nitrogen, reconstituted in 200 microL of DI water:acetonitrile (ACN) (75:25), and injected onto the UPLC/MS/MS for analysis. The increased speed and separation efficiency afforded by UPLC, allowed for the separation and subsequent quantification of both analytes in less than 2 min. Analytes were quantified using multiple reaction monitoring (MRM) and six-point calibration curves constructed in negative blood. Limits of detection for both analytes were 3 ng/g and the lower limit of quantitation (LLOQ) was 30 ng/g.

Improvements in High Speed, High Resolution Dynamic Digital Image Correlation for Experimental Evaluation of Composite Drive System Components

NASA Technical Reports Server (NTRS)

Kohlman, Lee W.; Ruggeri, Charles R.; Roberts, Gary D.; Handschuh, Robert Frederick

2013-01-01

Composite materials have the potential to reduce the weight of rotating drive system components. However, these components are more complex to design and evaluate than static structural components in part because of limited ability to acquire deformation and failure initiation data during dynamic tests. Digital image correlation (DIC) methods have been developed to provide precise measurements of deformation and failure initiation for material test coupons and for structures under quasi-static loading. Attempts to use the same methods for rotating components (presented at the AHS International 68th Annual Forum in 2012) are limited by high speed camera resolution, image blur, and heating of the structure by high intensity lighting. Several improvements have been made to the system resulting in higher spatial resolution, decreased image noise, and elimination of heating effects. These improvements include the use of a high intensity synchronous microsecond pulsed LED lighting system, different lenses, and changes in camera configuration. With these improvements, deformation measurements can be made during rotating component tests with resolution comparable to that which can be achieved in static tests

Improvements in High Speed, High Resolution Dynamic Digital Image Correlation for Experimental Evaluation of Composite Drive System Components

NASA Technical Reports Server (NTRS)

Kohlman, Lee; Ruggeri, Charles; Roberts, Gary; Handshuh, Robert

2013-01-01

Composite materials have the potential to reduce the weight of rotating drive system components. However, these components are more complex to design and evaluate than static structural components in part because of limited ability to acquire deformation and failure initiation data during dynamic tests. Digital image correlation (DIC) methods have been developed to provide precise measurements of deformation and failure initiation for material test coupons and for structures under quasi-static loading. Attempts to use the same methods for rotating components (presented at the AHS International 68th Annual Forum in 2012) are limited by high speed camera resolution, image blur, and heating of the structure by high intensity lighting. Several improvements have been made to the system resulting in higher spatial resolution, decreased image noise, and elimination of heating effects. These improvements include the use of a high intensity synchronous microsecond pulsed LED lighting system, different lenses, and changes in camera configuration. With these improvements, deformation measurements can be made during rotating component tests with resolution comparable to that which can be achieved in static tests.

Modulation bandwidth of spin torque oscillators under current modulation

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

Quinsat, M.; CEA, INAC-SPINTEC, F-38054 Grenoble; CNRS, SPINTEC, F-38054 Grenoble

2014-10-13

For practical applications of spin torque nano-oscillators (STNO), one of the most critical characteristics is the speed at which an STNO responds to variations of external control parameters, such as current or/and field. Theory predicts that this speed is limited by the amplitude relaxation rate Γ{sub p} that determines the timescale over which the amplitude fluctuations are damped out. In this study, this limit is verified experimentally by analyzing the amplitude and frequency noise spectra of the output voltage signal when modulating an STNO by a microwave current. In particular, it is shown that due to the non-isochronous nature ofmore » the STNO the amplitude relaxation rate Γ{sub p} determines not only the bandwidth of an amplitude modulation, but also the bandwidth of a frequency modulation. The presented experimental technique will be important for the optimisation of the STNO characteristics for applications in telecommunications or/and data storage and is applicable even in the case when the STNO output signal is only several times higher than noise.« less

A study on model fidelity for model predictive control-based obstacle avoidance in high-speed autonomous ground vehicles

NASA Astrophysics Data System (ADS)

Liu, Jiechao; Jayakumar, Paramsothy; Stein, Jeffrey L.; Ersal, Tulga

2016-11-01

This paper investigates the level of model fidelity needed in order for a model predictive control (MPC)-based obstacle avoidance algorithm to be able to safely and quickly avoid obstacles even when the vehicle is close to its dynamic limits. The context of this work is large autonomous ground vehicles that manoeuvre at high speed within unknown, unstructured, flat environments and have significant vehicle dynamics-related constraints. Five different representations of vehicle dynamics models are considered: four variations of the two degrees-of-freedom (DoF) representation as lower fidelity models and a fourteen DoF representation with combined-slip Magic Formula tyre model as a higher fidelity model. It is concluded that the two DoF representation that accounts for tyre nonlinearities and longitudinal load transfer is necessary for the MPC-based obstacle avoidance algorithm in order to operate the vehicle at its limits within an environment that includes large obstacles. For less challenging environments, however, the two DoF representation with linear tyre model and constant axle loads is sufficient.

Speed limits set lower than engineering recommendations.

DOT National Transportation Integrated Search

2016-08-01

The purpose of this project is to provide the Montana Department of Transportation (MDT) with a better understanding of the : operational and safety impacts of setting posted speed limits below engineering recommended values. This practice has been :...

Rural variable speed limits : phase II.

DOT National Transportation Integrated Search

2012-05-01

The Wyoming Department of Transportation (WYDOT) installed its first variable speed limit (VSL) corridor along : Interstate 80 in the Elk Mountain Corridor in the Spring of 2009 in an effort to improve safety and reduce road closures, : particularly ...

Index of mechanical work in gait of children with cerebral palsy.

PubMed

Dziuba, Alicja Katarzyna; Tylkowska, Małgorzata; Jaroszczuk, Sebastian

2014-01-01

The pathological gait of children with cerebral palsy involves higher mechanical work, which limits their ability to function properly in society. Mechanical work is directly related to walking speed and, although a number of studies have been carried out in this field, few of them analysed the effect of the speed. The study aimed to develop standards for mechanical work during gait of children with cerebral palsy depending on the walking speed. The study covered 18 children with cerebral palsy and 14 healthy children. The BTS Smart software and the author's software were used to evaluate mechanical work, kinetic, potential and rotational energy connected with motion of the children body during walk. Compared to healthy subjects, mechanical work in children with cerebral palsy increases with the degree of disability. It can be expressed as a linear function of walking speed and shows strong and statistically significant correlations with walking gait. A negative statistically significant correlation between the degree of disability and walking speed can be observed. The highest contribution to the total mechanical energy during gait is from mechanical energy of the feet. Instantaneous value of rotational energy is 700 times lower than the instantaneous mechanical energy. An increase in walking speed causes the increase in the effect of the index of kinetic energy on total mechanical work. The method described can provide an objective supplementation for doctors and physical therapists to perform a simple and immediate diagnosis without much technical knowledge.

Influence of Wind Speed on RGB-D Images in Tree Plantations

PubMed Central

Andújar, Dionisio; Dorado, José; Bengochea-Guevara, José María; Conesa-Muñoz, Jesús; Fernández-Quintanilla, César; Ribeiro, Ángela

2017-01-01

Weather conditions can affect sensors’ readings when sampling outdoors. Although sensors are usually set up covering a wide range of conditions, their operational range must be established. In recent years, depth cameras have been shown as a promising tool for plant phenotyping and other related uses. However, the use of these devices is still challenged by prevailing field conditions. Although the influence of lighting conditions on the performance of these cameras has already been established, the effect of wind is still unknown. This study establishes the associated errors when modeling some tree characteristics at different wind speeds. A system using a Kinect v2 sensor and a custom software was tested from null wind speed up to 10 m·s−1. Two tree species with contrasting architecture, poplars and plums, were used as model plants. The results showed different responses depending on tree species and wind speed. Estimations of Leaf Area (LA) and tree volume were generally more consistent at high wind speeds in plum trees. Poplars were particularly affected by wind speeds higher than 5 m·s−1. On the contrary, height measurements were more consistent for poplars than for plum trees. These results show that the use of depth cameras for tree characterization must take into consideration wind conditions in the field. In general, 5 m·s−1 (18 km·h−1) could be established as a conservative limit for good estimations. PMID:28430119

Accuracy of a step counter during treadmill and daily life walking by healthy adults and patients with cardiac disease

PubMed Central

Thorup, Charlotte Brun; Grønkjær, Mette; Dinesen, Birthe Irene

2017-01-01

Background Step counters have been used to observe activity and support physical activity, but there is limited evidence on their accuracy. Objective The purpose was to investigate the step accuracy of the Fitbit Zip (Zip) in healthy adults during treadmill walking and in patients with cardiac disease while hospitalised at home. Methods Twenty healthy adults aged 39±13.79 (mean ±SD) wore four Zips while walking on a treadmill at different speeds (1.7–6.1 km/hour), and 24 patients with cardiac disease (age 67±10.03) wore a Zip for 24 hours during hospitalisation and for 4 weeks thereafter at home. A Shimmer3 device was used as a criterion standard. Results At a treadmill speed of 3.6 km/hour, the relative error (±SD) for the Zips on the upper body was −0.02±0.67 on the right side and −0.09 (0.67) on the left side. For the Zips on the waist, this was 0.08±0.71 for the right side and -0.08 (0.47) on the left side. At a treadmill speed of 3.6 km/hour and higher, the average per cent of relative error was <3%. The 24-hour test for the hospitalised patients showed a relative error of −47.15±24.11 (interclass correlation coefficient (ICC): 0.60), and for the 24-hour test at home, the relative error was −27.51±28.78 (ICC: 0.87). Thus, none of the 24-hour tests had less than the expected 20% error. In time periods of evident walking during the 24 h test, the Zip had an average per cent relative error of <3% at 3.6 km/hour and higher speeds. Conclusions A speed of 3.6 km/hour or higher is required to expect acceptable accuracy in step measurement using a Zip, on a treadmill and in real life. Inaccuracies are directly related to slow speeds, which might be a problem for patients with cardiac disease who walk at a slow pace. PMID:28363918

Extending the boundaries of the Declaration of Helsinki: a case study of an unethical experiment in a non-medical setting

PubMed Central

Richter, E.; Barach, P.; Berman, T.; Ben-David, G; Weinberger, Z.

2001-01-01

To examine the ethical issues involved in governmental decisions with potential health risks, we review the history of the decision to raise the interurban speed limit in Israel in light of its impact on road death and injury. In 1993, the Israeli Ministry of Transportation initiated an "experiment" to raise the interurban speed limit from 90 to 100 kph. The "experiment" did not include a protocol and did not specify cut-off points for early termination in the case of adverse results. After the raise in the speed limit, the death toll on interurban roads rose as a result of a sudden increase in speeds and case fatality rates. The committee's decision is a case study in unfettered human experimentation and public health risks when the setting is non-medical and lacks a defined ethical framework. The case study states the case for extending Helsinki type safeguards to experimentation in non-medical settings. Key Words: Declaration of Helsinki • human experimentation • speed limit PMID:11314157

A machine learning approach for gait speed estimation using skin-mounted wearable sensors: From healthy controls to individuals with multiple sclerosis.

PubMed

McGinnis, Ryan S; Mahadevan, Nikhil; Moon, Yaejin; Seagers, Kirsten; Sheth, Nirav; Wright, John A; DiCristofaro, Steven; Silva, Ikaro; Jortberg, Elise; Ceruolo, Melissa; Pindado, Jesus A; Sosnoff, Jacob; Ghaffari, Roozbeh; Patel, Shyamal

2017-01-01

Gait speed is a powerful clinical marker for mobility impairment in patients suffering from neurological disorders. However, assessment of gait speed in coordination with delivery of comprehensive care is usually constrained to clinical environments and is often limited due to mounting demands on the availability of trained clinical staff. These limitations in assessment design could give rise to poor ecological validity and limited ability to tailor interventions to individual patients. Recent advances in wearable sensor technologies have fostered the development of new methods for monitoring parameters that characterize mobility impairment, such as gait speed, outside the clinic, and therefore address many of the limitations associated with clinical assessments. However, these methods are often validated using normal gait patterns; and extending their utility to subjects with gait impairments continues to be a challenge. In this paper, we present a machine learning method for estimating gait speed using a configurable array of skin-mounted, conformal accelerometers. We establish the accuracy of this technique on treadmill walking data from subjects with normal gait patterns and subjects with multiple sclerosis-induced gait impairments. For subjects with normal gait, the best performing model systematically overestimates speed by only 0.01 m/s, detects changes in speed to within less than 1%, and achieves a root-mean-square-error of 0.12 m/s. Extending these models trained on normal gait to subjects with gait impairments yields only minor changes in model performance. For example, for subjects with gait impairments, the best performing model systematically overestimates speed by 0.01 m/s, quantifies changes in speed to within 1%, and achieves a root-mean-square-error of 0.14 m/s. Additional analyses demonstrate that there is no correlation between gait speed estimation error and impairment severity, and that the estimated speeds maintain the clinical significance of ground truth speed in this population. These results support the use of wearable accelerometer arrays for estimating walking speed in normal subjects and their extension to MS patient cohorts with gait impairment.

High Technology Centrifugal Compressor for Commercial Air Conditioning Systems

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

Ruckes, John

2006-04-15

R&D Dynamics, Bloomfield, CT in partnership with the State of Connecticut has been developing a high technology, oil-free, energy-efficient centrifugal compressor called CENVA for commercial air conditioning systems under a program funded by the US Department of Energy. The CENVA compressor applies the foil bearing technology used in all modern aircraft, civil and military, air conditioning systems. The CENVA compressor will enhance the efficiency of water and air cooled chillers, packaged roof top units, and other air conditioning systems by providing an 18% reduction in energy consumption in the unit capacity range of 25 to 350 tons of refrigeration Themore » technical approach for CENVA involved the design and development of a high-speed, oil-free foil gas bearing-supported two-stage centrifugal compressor, CENVA encompassed the following high technologies, which are not currently utilized in commercial air conditioning systems: Foil gas bearings operating in HFC-134a; Efficient centrifugal impellers and diffusers; High speed motors and drives; and System integration of above technologies. Extensive design, development and testing efforts were carried out. Significant accomplishments achieved under this program are: (1) A total of 26 builds and over 200 tests were successfully completed with successively improved designs; (2) Use of foil gas bearings in refrigerant R134a was successfully proven; (3) A high speed, high power permanent magnet motor was developed; (4) An encoder was used for signal feedback between motor and controller. Due to temperature limitations of the encoder, the compressor could not operate at higher speed and in turn at higher pressure. In order to alleviate this problem a unique sensorless controller was developed; (5) This controller has successfully been tested as stand alone; however, it has not yet been integrated and tested as a system; (6) The compressor successfully operated at water cooled condensing temperatures Due to temperature limitations of the encoder, it could not be operated at air cooled condensing temperatures. (7) The two-stage impellers/diffusers worked well separately but combined did not match well.« less

A Vehicular Mobile Standard Instrument for Field Verification of Traffic Speed Meters Based on Dual-Antenna Doppler Radar Sensor

PubMed Central

Du, Lei; Sun, Qiao; Cai, Changqing; Bai, Jie; Fan, Zhe; Zhang, Yue

2018-01-01

Traffic speed meters are important legal measuring instruments specially used for traffic speed enforcement and must be tested and verified in the field every year using a vehicular mobile standard speed-measuring instrument to ensure speed-measuring performances. The non-contact optical speed sensor and the GPS speed sensor are the two most common types of standard speed-measuring instruments. The non-contact optical speed sensor requires extremely high installation accuracy, and its speed-measuring error is nonlinear and uncorrectable. The speed-measuring accuracy of the GPS speed sensor is rapidly reduced if the amount of received satellites is insufficient enough, which often occurs in urban high-rise regions, tunnels, and mountainous regions. In this paper, a new standard speed-measuring instrument using a dual-antenna Doppler radar sensor is proposed based on a tradeoff between the installation accuracy requirement and the usage region limitation, which has no specified requirements for its mounting distance and no limitation on usage regions and can automatically compensate for the effect of an inclined installation angle on its speed-measuring accuracy. Theoretical model analysis, simulated speed measurement results, and field experimental results compared with a GPS speed sensor with high accuracy showed that the dual-antenna Doppler radar sensor is effective and reliable as a new standard speed-measuring instrument. PMID:29621142

A Vehicular Mobile Standard Instrument for Field Verification of Traffic Speed Meters Based on Dual-Antenna Doppler Radar Sensor.

PubMed

Du, Lei; Sun, Qiao; Cai, Changqing; Bai, Jie; Fan, Zhe; Zhang, Yue

2018-04-05

Traffic speed meters are important legal measuring instruments specially used for traffic speed enforcement and must be tested and verified in the field every year using a vehicular mobile standard speed-measuring instrument to ensure speed-measuring performances. The non-contact optical speed sensor and the GPS speed sensor are the two most common types of standard speed-measuring instruments. The non-contact optical speed sensor requires extremely high installation accuracy, and its speed-measuring error is nonlinear and uncorrectable. The speed-measuring accuracy of the GPS speed sensor is rapidly reduced if the amount of received satellites is insufficient enough, which often occurs in urban high-rise regions, tunnels, and mountainous regions. In this paper, a new standard speed-measuring instrument using a dual-antenna Doppler radar sensor is proposed based on a tradeoff between the installation accuracy requirement and the usage region limitation, which has no specified requirements for its mounting distance and no limitation on usage regions and can automatically compensate for the effect of an inclined installation angle on its speed-measuring accuracy. Theoretical model analysis, simulated speed measurement results, and field experimental results compared with a GPS speed sensor with high accuracy showed that the dual-antenna Doppler radar sensor is effective and reliable as a new standard speed-measuring instrument.

Optimisation of sprinting performance in running, cycling and speed skating.

PubMed

van Ingen Schenau, G J; de Koning, J J; de Groot, G

1994-04-01

Sprinting performances rely strongly on a fast acceleration at the start of a sprint and on the capacity to maintain a high velocity in the phase following the start. Simulations based on a model developed in which the generation of metabolic power is related to the mechanical destinations of power showed that for short-lasting sprinting events, the best pacing strategy is an all out effort, even if this strategy causes a strong reduction of the velocity at the end of the race. Even pacing strategies should only be used in exercises lasting longer than 80 to 100 seconds. Sprint runners, speed skaters and cyclists need a large rate of breakdown of energy rich phosphates in the first 4 to 5 seconds of the race (mechanical equivalent > 20 W/kg) in order to accelerate their body, and a power output of more than 10 W/kg in the phase following the start to maintain a high velocity. Maximal speed in running is mainly limited by the necessity to rotate the legs forwards and backwards relative to the hip joint. The acceleration phase, however, relies on powerful extensions of all leg joints. Through a comparison of the hindlimb design of highly specialised animal sprinters (as can be found among predators) and of long distance animal runners (as found among hoofed animals), it is illustrated that these 2 phases of a sprint rely on conflicting requirements: improvement of maximal speed would require lower moments of inertia of the legs whereas a faster acceleration would require the involvement of more muscle mass (not only of the hip and knee extensors but also of the plantar flexors). Maximal speed in cycling and speed skating is not limited by the necessity to move leg segments but rather on air friction and rolling or ice friction. Since the drag coefficients found for speed skaters and cyclists (about 0.8) are considerably higher than those of more streamlined bodies, much progress can still be expected from the reduction of air friction. Speed skaters and especially cyclists show much smaller accelerations during the start than do sprint runners. Skaters might try to improve their very first push off by developing a start technique that allows a much more horizontally directed propulsive force. The small propulsive force at the onset of a cycling sprint is due to the gearing system.(ABSTRACT TRUNCATED AT 400 WORDS)

Alternative Fuels Data Center

Science.gov Websites

Low-Speed Vehicle Access to Roadways Low-speed vehicles are only permitted on highways with speed limits up to 35 miles per hour (mph) or up to 45 mph in some municipalities or boroughs. Low-speed highway that allows low-speed vehicle use. Operators of low-speed vehicles are subject to all traffic laws

Takeoff certification considerations for large subsonic and supersonic transport airplanes using the Ames flight simulator for advanced aircraft

NASA Technical Reports Server (NTRS)

Snyder, C. T.; Drinkwater, F. J., III; Fry, E. B.; Forrest, R. D.

1973-01-01

Data for use in development of takeoff airworthiness standards for new aircraft designs such as the supersonic transport (SST) and the large wide-body subsonic jet transport are provided. An advanced motion simulator was used to compare the performance and handling characteristics of three representative large jet transports during specific flight certification tasks. Existing regulatory constraints and methods for determining rotation speed were reviewed, and the effects on takeoff performance of variations in rotation speed, pitch attitude, and pitch attitude rate during the rotation maneuver were analyzed. A limited quantity of refused takeoff information was obtained. The aerodynamics, wing loading, and thrust-to-weight ratio of the subject SST resulted in takeoff speeds limited by climb (rather than lift-off) considerations. Take-off speeds based on U.S. subsonic transport requirements were found unacceptable because of the criticality of rotation-abuse effects on one-engine-inoperative climb performance. Adequate safety margin was provided by takeoff speeds based on proposed Anglo-French supersonic transport (TSS) criteria, with the limiting criterion being that takeoff safety speed be at least 1.15 times the one-engine-inoperative zero-rate-of-climb speed. Various observations related to SST certification are presented.

Hydrodynamic Characteristics of a Low-drag, Planing-tail Flying-boat Hull

NASA Technical Reports Server (NTRS)

Suydam, Henry B

1948-01-01

The hydrodynamic characteristics of a flying-boat incorporating a low-drag, planing-tail hull were determined from model tests made in Langley tank number 2 and compared with tests of the same flying boat incorporating a conventional-type hull. The planing-tail model, with which stable take-offs were possible for a large range of elevator positions at all center-of-gravity locations tested, had more take-off stability than the conventional model. No upper-limit porpoising was encountered by the planing-tail model. The maximum changes in rise during landings were lower for the planing-tail model than for the conventional model at most contact trims, an indication of improved landing stability for the planing-tail model. The hydrodynamic resistance of the planing-tail hull was lower than the conventional hull at all speeds, and the load-resistance ratio was higher for the planing-tail hull, being especially high at the hump. The static trim of the planing-tail hull was much higher than the conventional hull, but the variation of trim with speed during take-off was smaller.

Feedback interventions and driving speed: A parametric and comparative analysis

PubMed Central

Houten, Ron Van; Nau, Paul A.

1983-01-01

Five experiments were conducted to assess the effects of several variables on the efficacy of feedback in reducing driving speed. Experiment 1 systematically varied the criterion used to define speeding, and results showed that the use of a lenient criterion (20 km/hr over the speed limit), which allowed for the posting of high percentages of drivers not speeding, was more effective in reducing speeding than the use of a stringent criterion (10 km/hr over the speed limit). In Experiment 2 an analysis revealed that posting feedback reduced speeding on a limited access highway and the effects persisted to some degree up to 6 km. Experiments 3 and 4 compared the effectiveness of an unmanned parked police vehicle (Experiment 3) and a police air patrol speeding program (Experiment 4) with the feedback sign and determined whether the presence of either of these enforcement variables could potentiate the efficacy of the sign. The results of both experiments demonstrated that although the two enforcement programs initially produced larger effects than the feedback sign, the magnitude of their effect attenuated over time. Experiment 5 compared the effectiveness of a traditional enforcement program with a warning program which included handing out a flier providing feedback on the number and types of accidents occuring on the road during the past year. This experiment demonstrated that the warning program produced a marked reduction in speeding and the traditional enforcement program did not. Furthermore, the warning program and a feedback sign together produced an even greater reduction in speeding than either alone. PMID:16795666

Guidelines for Speed Reduction in Towns Along Rural Highways

DOT National Transportation Integrated Search

2013-10-01

This report presents the results of the study undertaken to develop a guideline for setting up speed limit in towns along rural highways of Nevada. Generally, speed zones are provided in towns along rural highways to reduce speed-related crashes. How...

Excitability of the Primary Motor Cortex Increases More Strongly with Slow- than with Normal-Speed Presentation of Actions

PubMed Central

Moriuchi, Takefumi; Iso, Naoki; Sagari, Akira; Ogahara, Kakuya; Kitajima, Eiji; Tanaka, Koji; Tabira, Takayuki; Higashi, Toshio

2014-01-01

Introduction The aim of the present study was to investigate how the speed of observed action affects the excitability of the primary motor cortex (M1), as assessed by the size of motor evoked potentials (MEPs) induced by transcranial magnetic stimulation (TMS). Methods Eighteen healthy subjects watched a video clip of a person catching a ball, played at three different speeds (normal-, half-, and quarter-speed). MEPs were induced by TMS when the model's hand had opened to the widest extent just before catching the ball (“open”) and when the model had just caught the ball (“catch”). These two events were locked to specific frames of the video clip (“phases”), rather than occurring at specific absolute times, so that they could easily be compared across different speeds. MEPs were recorded from the thenar (TH) and abductor digiti minimi (ADM) muscles of the right hand. Results The MEP amplitudes were higher when the subjects watched the video clip at low speed than when they watched the clip at normal speed. A repeated-measures ANOVA, with the factor VIDEO-SPEED, showed significant main effects. Bonferroni's post hoc test showed that the following MEP amplitude differences were significant: TH, normal vs. quarter; ADM, normal vs. half; and ADM, normal vs. quarter. Paired t-tests showed that the significant MEP amplitude differences between TMS phases under each speed condition were TH, “catch” higher than “open” at quarter speed; ADM, “catch” higher than “open” at half speed. Conclusions These results indicate that the excitability of M1 was higher when the observed action was played at low speed. Our findings suggest that the action observation system became more active when the subjects observed the video clip at low speed, because the subjects could then recognize the elements of action and intention in others. PMID:25479161

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

Critchlow, Terence J.; Abdulla, Ghaleb; Becla, Jacek

Data management is the organization of information to support efficient access and analysis. For data intensive computing applications, the speed at which relevant data can be accessed is a limiting factor in terms of the size and complexity of computation that can be performed. Data access speed is impacted by the size of the relevant subset of the data, the complexity of the query used to define it, and the layout of the data relative to the query. As the underlying data sets become increasingly complex, the questions asked of it become more involved as well. For example, geospatial datamore » associated with a city is no longer limited to the map data representing its streets, but now also includes layers identifying utility lines, key points, locations and types of businesses within the city limits, tax information for each land parcel, satellite imagery, and possibly even street-level views. As a result, queries have gone from simple questions, such as "how long is Main Street?", to much more complex questions such as "taking all other factors into consideration, are the property values of houses near parks higher than those under power lines, and if so, by what percentage". Answering these questions requires a coherent infrastructure, integrating the relevant data into a format optimized for the questions being asked.« less

Compressor discharge film riding face seals

NASA Technical Reports Server (NTRS)

Munson, John

1994-01-01

Seals examined were the eight-pad Rayleigh step, the tapered spiral groove, and two hydrostatic seals. The spiral groove configuration is the preferred choice because of superior stiffness. Second choice is Rayleigh step because of combined higher operating film thickness and good stiffness at low clearance. Recess hydrostatic has reasonable performance, but stiffness falls off at low clearance. Also, pneumatic hammer characteristics must be investigated. Experience at high pressure ratios is limited. An advantage is that it would have good low speed performance.

Wind speed response of marine non-precipitating stratocumulus clouds over a diurnal cycle in cloud-system resolving simulations

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

Kazil, Jan; Feingold, Graham; Yamaguchi, Takanobu

Observed and projected trends in large-scale wind speed over the oceans prompt the question: how do marine stratocumulus clouds and their radiative properties respond to changes in large-scale wind speed? Wind speed drives the surface fluxes of sensible heat, moisture, and momentum and thereby acts on cloud liquid water path (LWP) and cloud radiative properties. We present an investigation of the dynamical response of non-precipitating, overcast marine stratocumulus clouds to different wind speeds over the course of a diurnal cycle, all else equal. In cloud-system resolving simulations, we find that higher wind speed leads to faster boundary layer growth and strongermore » entrainment. The dynamical driver is enhanced buoyant production of turbulence kinetic energy (TKE) from latent heat release in cloud updrafts. LWP is enhanced during the night and in the morning at higher wind speed, and more strongly suppressed later in the day. Wind speed hence accentuates the diurnal LWP cycle by expanding the morning–afternoon contrast. The higher LWP at higher wind speed does not, however, enhance cloud top cooling because in clouds with LWP ≳50 gm –2, longwave emissions are insensitive to LWP. This leads to the general conclusion that in sufficiently thick stratocumulus clouds, additional boundary layer growth and entrainment due to a boundary layer moistening arises by stronger production of TKE from latent heat release in cloud updrafts, rather than from enhanced longwave cooling. Here, we find that large-scale wind modulates boundary layer decoupling. At nighttime and at low wind speed during daytime, it enhances decoupling in part by faster boundary layer growth and stronger entrainment and in part because shear from large-scale wind in the sub-cloud layer hinders vertical moisture transport between the surface and cloud base. With increasing wind speed, however, in decoupled daytime conditions, shear-driven circulation due to large-scale wind takes over from buoyancy-driven circulation in transporting moisture from the surface to cloud base and thereby reduces decoupling and helps maintain LWP. Furthermore, the total (shortwave + longwave) cloud radiative effect (CRE) responds to changes in LWP and cloud fraction, and higher wind speed translates to a stronger diurnally averaged total CRE. However, the sensitivity of the diurnally averaged total CRE to wind speed decreases with increasing wind speed.« less

Wind speed response of marine non-precipitating stratocumulus clouds over a diurnal cycle in cloud-system resolving simulations

DOE PAGES

Kazil, Jan; Feingold, Graham; Yamaguchi, Takanobu

2016-05-12

Observed and projected trends in large-scale wind speed over the oceans prompt the question: how do marine stratocumulus clouds and their radiative properties respond to changes in large-scale wind speed? Wind speed drives the surface fluxes of sensible heat, moisture, and momentum and thereby acts on cloud liquid water path (LWP) and cloud radiative properties. We present an investigation of the dynamical response of non-precipitating, overcast marine stratocumulus clouds to different wind speeds over the course of a diurnal cycle, all else equal. In cloud-system resolving simulations, we find that higher wind speed leads to faster boundary layer growth and strongermore » entrainment. The dynamical driver is enhanced buoyant production of turbulence kinetic energy (TKE) from latent heat release in cloud updrafts. LWP is enhanced during the night and in the morning at higher wind speed, and more strongly suppressed later in the day. Wind speed hence accentuates the diurnal LWP cycle by expanding the morning–afternoon contrast. The higher LWP at higher wind speed does not, however, enhance cloud top cooling because in clouds with LWP ≳50 gm –2, longwave emissions are insensitive to LWP. This leads to the general conclusion that in sufficiently thick stratocumulus clouds, additional boundary layer growth and entrainment due to a boundary layer moistening arises by stronger production of TKE from latent heat release in cloud updrafts, rather than from enhanced longwave cooling. Here, we find that large-scale wind modulates boundary layer decoupling. At nighttime and at low wind speed during daytime, it enhances decoupling in part by faster boundary layer growth and stronger entrainment and in part because shear from large-scale wind in the sub-cloud layer hinders vertical moisture transport between the surface and cloud base. With increasing wind speed, however, in decoupled daytime conditions, shear-driven circulation due to large-scale wind takes over from buoyancy-driven circulation in transporting moisture from the surface to cloud base and thereby reduces decoupling and helps maintain LWP. Furthermore, the total (shortwave + longwave) cloud radiative effect (CRE) responds to changes in LWP and cloud fraction, and higher wind speed translates to a stronger diurnally averaged total CRE. However, the sensitivity of the diurnally averaged total CRE to wind speed decreases with increasing wind speed.« less

Factors associated with gait speed recovery after total knee arthroplasty: A longitudinal study.

PubMed

Pua, Yong-Hao; Seah, Felicia Jie-Ting; Clark, Ross Allan; Lian-Li Poon, Cheryl; Tan, John Wei-Ming; Chong, Hwei-Chi

2017-04-01

Gait speed limitations can remain significant issues after a total knee arthroplasty (TKA) but their associated factors are not well understood. This study aimed to identify the factors associated with acute gait speed recovery post-TKA. We performed a prospective longitudinal study of 1765 patients who underwent primary TKA between July 2013 and July 2015. At 4, 8, 12, and 16 weeks postsurgery, fast gait speed was measured. The factors associated with gait speed over time since TKA were identified using multivariable generalized least squares modeling. Lower postoperative quadriceps strength and knee flexion range of motion were closely associated with lower gait speed over time (0.084m/s, 0.064m/s, and 0.055m/s change in gait speed per interquartile range change in ipsilateral quadriceps strength, contralateral quadriceps strength, and knee flexion range of motion, respectively). Additional strong predictors of lower gait speed included older age (0.11m/s), lower levels of preoperative Short Form 36 physical function (0.066m/s), greater body mass (0.046m/s), and the preoperative use of a walking aid (overall P < 0.001). Patients who reported that they limited their daily activities due to a fear of falling also had poorer gait speed (0.033m/s and 0.054m/s slower gait speed for "Occasional" and "Often" categories, respectively, vs. "None"). Gait speed recovery post-TKA is driven by both physical and psychological factors, suggesting that identifying and treating the underlying physical and cognitive causes of gait speed limitations may be crucial to optimize functional recovery. Copyright © 2017 Elsevier Inc. All rights reserved.

Additional road markings as an indication of speed limits: results of a field experiment and a driving simulator study.

PubMed

Daniels, Stijn; Vanrie, Jan; Dreesen, An; Brijs, Tom

2010-05-01

Although speed limits are indicated by road signs, road users are not always aware, while driving, of the actual speed limit on a given road segment. The Roads and Traffic Agency developed additional road markings in order to support driver decisions on speed on 70 km/h roads in Flanders-Belgium. In this paper the results are presented of two evaluation studies, both a field study and a simulator study, on the effects of the additional road markings on speed behaviour. The results of the field study showed no substantial effect of the markings on speed behaviour. Neither did the simulator study, with slightly different stimuli. Nevertheless an effect on lateral position was noticed in the simulator study, showing at least some effect of the markings. The role of conspicuity of design elements and expectations towards traffic environments is discussed. Both studies illustrate well some strengths and weaknesses of observational field studies compared to experimental simulator studies. Copyright (c) 2009 Elsevier Ltd. All rights reserved.

Some applications of equilibrium thermodynamic properties to continuum gasdynamics

NASA Technical Reports Server (NTRS)

1976-01-01

The speed of sound for the propagation of isentropic disturbances in a gas is developed, including corrections for chemical reaction. The term zero frequency is used to describe this isentropic limit sound speed; the term signifies that change in the gasdynamic variables are all very slow compared with the chemical rate changes in the gas. A faster, nonisentropic speed of propagation occurs for disturbances where the changes in gasdynamic variables are fast compared with the chemical rate changes. In the limit, this is known as the infinite frequency or frozen sound speed - the former term calling attention to the very high frequency of the disturbance, the latter term calling attention to the frozen character of the chemical reactions under such rapid changes of state. The true sound speed for a disturbance of finite frequency is shown to be between these two limits and is expressed in terms of the chemical relaxation time. The Riemann invariants that are useful in determining the changes in flow speed along characteristic directions in supersonic flow are derived in terms of integrations of acoustic impedance, and example results are given for air.

Unlabored system motion by specially conditioned electromagnetic fields in higher dimensional realms

NASA Astrophysics Data System (ADS)

David Froning, H.; Meholic, Gregory V.

2010-01-01

This third of three papers explores the possibility of swift, stress-less system transitions between slower-than-light and faster-than-light speeds with negligible net expenditure of system energetics. The previous papers derived a realm of higher dimensionality than 4-D spacetime that enabled such unlabored motion; and showed that fields that could propel and guide systems on unlabored paths in the higher dimensional realm must be fields that have been conditioned to SU(2) (or higher) Lie group symmetry. This paper shows that the system's surrounding vacuum dielectric ɛμ, within the higher dimensional realm's is a vector (not scalar) quantity with fixed magnitude ɛ0μ0 and changing direction within the realm with changing system speed. Thus, ɛμ generated by the system's EM field must remain tuned to vacuum ɛ0μ0 in both magnitude and direction during swift, unlabored system transitions between slower and faster than light speeds. As a result, the system's changing path and speed is such that the magnitude of the higher dimensional realm's ɛ0μ0 is not disturbed. And it is shown that a system's flight trajectories associated with its swift, unlabored transitions between zero and infinite speed can be represented by curved paths traced-out within the higher dimensional realm.

Fuzzy Variable Speed Limit Device Modification and Testing - Phase II

DOT National Transportation Integrated Search

2001-07-01

In a previous project, Northern Arizona University (NAU) and the Arizona Department of Transportation (ADOT) designed and implemented the prototype of a variable speed limit (VSL) system for rural highways. The VSL system implements a real-time fuzzy...

Limits on Lorentz Invariance Violation from Coulomb Interactions in Nuclei and Atoms.

PubMed

Flambaum, V V; Romalis, M V

2017-04-07

Anisotropy in the speed of light that has been constrained by Michelson-Morley-type experiments also generates anisotropy in the Coulomb interactions. This anisotropy can manifest itself as an energy anisotropy in nuclear and atomic experiments. Here the experimental limits on Lorentz violation in _{10}^{21}Ne are used to improve the limits on Lorentz symmetry violations in the photon sector, namely, the anisotropy of the speed of light and the Coulomb interactions, by 7 orders of magnitude in comparison with previous experiments: the speed of light is isotropic to a part in 10^{28}.

Intelligent Advisory Speed Limit Dedication in Highway Using VANET

PubMed Central

Md Noor, Rafidah; Yeo, Hwasoo; Jung, Jason J.

2014-01-01

Variable speed limits (VSLs) as a mean for enhancing road traffic safety are studied for decades to modify the speed limit based on the prevailing road circumstances. In this study the pros and cons of VSL systems and their effects on traffic controlling efficiency are summarized. Despite the potential effectiveness of utilizing VSLs, we have witnessed that the effectiveness of this system is impacted by factors such as VSL control strategy used and the level of driver compliance. Hence, the proposed approach called Intelligent Advisory Speed Limit Dedication (IASLD) as the novel VSL control strategy which considers the driver compliance aims to improve the traffic flow and occupancy of vehicles in addition to amelioration of vehicle's travel times. The IASLD provides the advisory speed limit for each vehicle exclusively based on the vehicle's characteristics including the vehicle type, size, and safety capabilities as well as traffic and weather conditions. The proposed approach takes advantage of vehicular ad hoc network (VANET) to accelerate its performance, in the way that simulation results demonstrate the reduction of incident detection time up to 31.2% in comparison with traditional VSL strategy. The simulation results similarly indicate the improvement of traffic flow efficiency, occupancy, and travel time in different conditions. PMID:24999493

Matching Countermeasures to Driver Types and Speeding Behavior : Traffic Tech

DOT National Transportation Integrated Search

2017-06-01

Speeding is a common behavior; most drivers exceed the speed limit some of the time. It is also a complicated behavior that varies by driver and situation. Speeding-related crashes take a large annual toll in injuries, lost lives, and high economic c...

Ways to estimate speeds for the purposes of air quality conformity analyses.

DOT National Transportation Integrated Search

2002-01-01

A speed post-processor refers to equations or lookup tables that can determine vehicle speeds on a particular roadway link using only the limited information available in a long-range planning model. An estimated link speed is usually based on volume...

Higher speed freight truck : structural analysis.

DOT National Transportation Integrated Search

2013-10-01

Sharma & Associates, Inc. (SA) had previously (20052009) developed a higher speed freight truck under sponsorship ofthe : Federal Railroad Administration (FRA). Under the current contract, SA wastasked with developing performance requirements : fo...

Extensibility and limitations of FDDI

NASA Technical Reports Server (NTRS)

Game, David; Maly, Kurt J.

1990-01-01

Recently two standards for Metropolitan Area Networks (MANs), Fiber Distributed Data Interface (FDDI) and Distributed Queue Dual Bus (DQDB), have emerged as the primary competitors for the MAN arena. Great interest exists in building higher speed networks which support large numbers of node and greater distance, and it is not clear what types of protocols are needed for this type of environment. There is some question as to whether or not these MAN standards can be extended to such environments. The extensibility of FDDI to the Gbps range and a long distance environment is investigated. Specification parameters which affect performance are shown and a measure is provided for predicting utilization of FDDI. A comparison of FDDI at 100 Mbps and 1 Gbps is presented. Some specific problems with FDDI are addressed and modifications which improve the viability of FDDI in such high speed networks are investigated.

Air Reactions to Objects Moving at Rates Above the Velocity of Sound with Application to the Air Propeller

NASA Technical Reports Server (NTRS)

Reed, S Albert

1922-01-01

There has been a tradition general among aeronautical engineers that a critical point exists for tip speeds at or near the velocity of sound, indicating a physical limit in the use of propellers at higher tip speeds; the idea being that something would occur analogous to what is known in marine propellers as cavitation. In the examination of the physics pertaining to both propellers and projectiles moving at or above 1100 feet per second, the conclusion was reached by the author that there is no reason for the existence of such a critical point and that, if it had been noted by observers it was not inherent in the phenomena revealed, but rather due to a particular shape or proportion of the projectile and that, with properly proportioned sections, it would not exist.

Pulsar current sheet C̆erenkov radiation

NASA Astrophysics Data System (ADS)

Zhang, Fan

2018-04-01

Plasma-filled pulsar magnetospheres contain thin current sheets wherein the charged particles are accelerated by magnetic reconnections to travel at ultra-relativistic speeds. On the other hand, the plasma frequency of the more regular force-free regions of the magnetosphere rests almost precisely on the upper limit of radio frequencies, with the cyclotron frequency being far higher due to the strong magnetic field. This combination produces a peculiar situation, whereby radio-frequency waves can travel at subluminal speeds without becoming evanescent. The conditions are thus conducive to C̆erenkov radiation originating from current sheets, which could plausibly serve as a coherent radio emission mechanism. In this paper we aim to provide a portrait of the relevant processes involved, and show that this mechanism can possibly account for some of the most salient features of the observed radio signals.

36 CFR 1192.175 - High-speed rail cars, monorails and systems.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 36 Parks, Forests, and Public Property 3 2010-07-01 2010-07-01 false High-speed rail cars... TRANSPORTATION VEHICLES Other Vehicles and Systems § 1192.175 High-speed rail cars, monorails and systems. (a) All cars for high-speed rail systems, including but not limited to those using “maglev” or high speed...

36 CFR 1192.175 - High-speed rail cars, monorails and systems.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 36 Parks, Forests, and Public Property 3 2012-07-01 2012-07-01 false High-speed rail cars... TRANSPORTATION VEHICLES Other Vehicles and Systems § 1192.175 High-speed rail cars, monorails and systems. (a) All cars for high-speed rail systems, including but not limited to those using “maglev” or high speed...

36 CFR 1192.175 - High-speed rail cars, monorails and systems.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 36 Parks, Forests, and Public Property 3 2011-07-01 2011-07-01 false High-speed rail cars... TRANSPORTATION VEHICLES Other Vehicles and Systems § 1192.175 High-speed rail cars, monorails and systems. (a) All cars for high-speed rail systems, including but not limited to those using “maglev” or high speed...

36 CFR § 1192.175 - High-speed rail cars, monorails and systems.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 36 Parks, Forests, and Public Property 3 2013-07-01 2012-07-01 true High-speed rail cars... TRANSPORTATION VEHICLES Other Vehicles and Systems § 1192.175 High-speed rail cars, monorails and systems. (a) All cars for high-speed rail systems, including but not limited to those using “maglev” or high speed...

36 CFR 1192.175 - High-speed rail cars, monorails and systems.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 36 Parks, Forests, and Public Property 3 2014-07-01 2014-07-01 false High-speed rail cars... TRANSPORTATION VEHICLES Other Vehicles and Systems § 1192.175 High-speed rail cars, monorails and systems. (a) All cars for high-speed rail systems, including but not limited to those using “maglev” or high speed...

14 CFR 25.1511 - Flap extended speed.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Flap extended speed. 25.1511 Section 25... Limitations § 25.1511 Flap extended speed. The established flap extended speed V FE must be established so that it does not exceed the design flap speed V F chosen under §§ 25.335(e) and 25.345, for the...

14 CFR 25.1517 - Rough air speed, VRA.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Rough air speed, VRA. 25.1517 Section 25... Limitations § 25.1517 Rough air speed, VRA. A rough air speed, VRA, for use as the recommended turbulence... specified in § 25.335(d); and (3) Is sufficiently less than VMO to ensure that likely speed variation during...

14 CFR 25.1511 - Flap extended speed.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Flap extended speed. 25.1511 Section 25... Limitations § 25.1511 Flap extended speed. The established flap extended speed V FE must be established so that it does not exceed the design flap speed V F chosen under §§ 25.335(e) and 25.345, for the...

14 CFR 25.1517 - Rough air speed, VRA.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Rough air speed, VRA. 25.1517 Section 25... Limitations § 25.1517 Rough air speed, VRA. A rough air speed, VRA, for use as the recommended turbulence... specified in § 25.335(d); and (3) Is sufficiently less than VMO to ensure that likely speed variation during...

Local quenches and quantum chaos from higher spin perturbations

NASA Astrophysics Data System (ADS)

David, Justin R.; Khetrapal, Surbhi; Kumar, S. Prem

2017-10-01

We study local quenches in 1+1 dimensional conformal field theories at large- c by operators carrying higher spin charge. Viewing such states as solutions in Chern-Simons theory, representing infalling massive particles with spin-three charge in the BTZ back-ground, we use the Wilson line prescription to compute the single-interval entanglement entropy (EE) and scrambling time following the quench. We find that the change in EE is finite (and real) only if the spin-three charge q is bounded by the energy of the perturbation E, as | q| /c < E 2 /c 2. We show that the Wilson line/EE correlator deep in the quenched regime and its expansion for small quench widths overlaps with the Regge limit for chaos of the out-of-time-ordered correlator. We further find that the scrambling time for the two-sided mutual information between two intervals in the thermofield double state increases with increasing spin-three charge, diverging when the bound is saturated. For larger values of the charge, the scrambling time is shorter than for pure gravity and controlled by the spin-three Lyapunov exponent 4 π/β. In a CFT with higher spin chemical potential, dual to a higher spin black hole, we find that the chemical potential must be bounded to ensure that the mutual information is a concave function of time and entanglement speed is less than the speed of light. In this case, a quench with zero higher spin charge yields the same Lyapunov exponent as pure Einstein gravity.

Predictors of change in physical function among older adults in response to long-term, structured physical activity: The LIFE Study

PubMed Central

Layne, Andrew S.; Hsu, Fang-Chi; Blair, Steven N.; Chen, Shyh-Huei; Dungan, Jennifer; Fielding, Roger A.; Glynn, Nancy W.; Hajduk, Alexandra M.; King, Abby C.; Manini, Todd M.; Marsh, Anthony P.; Pahor, Marco; Pellegrini, Christine A.; Buford, Thomas W.

2016-01-01

Objective To evaluate the extent of variability in functional responses among participants in the LIFE study, and to identify the relative contributions of intervention adherence, physical activity, and demographic and health characteristics to this variability. Design Secondary analysis of the Lifestyle Interventions and Independence for Elders (LIFE) study. Setting Multicenter U.S. institutions participating in the LIFE study. Participants A volunteer sample of 1635 sedentary men and women aged 70 to 89 years who were able to walk 400 m, but had physical limitations, defined as a score on the Short Physical Performance Battery (SPPB) of ≤9. Interventions Moderate-intensity physical activity (PA, n=818) consisting of aerobic, resistance and flexibility exercises performed both center-based (twice/wk) and in or around the home environment (3-4 times/wk) or health education (HE, n=817) consisting of weekly to monthly workshops covering relevant health information. Main Outcome Measures Physical function: gait speed over 400-m and lower extremity function (SPPB) assessed at baseline, six, twelve, and 24 months. Results Greater baseline physical function (gait speed and SPPB score) was inversely associated with Δ gait speed (regression coefficient β=−0.185, p<0.001) and ΔSPPB score (β=−0.365, p<0.001), while greater number of steps per day measured by accelerometry was positively associated with Δ gait speed (β=0.035, p<0.001) and Δ SPPB score (β=0.525, p<0.001). Other baseline factors associated with positive Δ gait speed and/or SPPB score include younger age (p<0.001), lower body mass index (p<0.001), and higher self-reported physical activity (p=0.002). Conclusions Several demographic and physical activity-related factors were associated with the extent of Δ functional outcomes among participants in the LIFE study. These factors should be considered when designing interventions for improving physical function among older adults with limited mobility. PMID:27568165

Inhibition of bubble coalescence: effects of salt concentration and speed of approach.

PubMed

Del Castillo, Lorena A; Ohnishi, Satomi; Horn, Roger G

2011-04-01

Bubble coalescence experiments have been performed using a sliding bubble apparatus, in which mm-sized bubbles in an aqueous electrolyte solution without added surfactant rose toward an air meniscus at different speeds obtained by varying the inclination of a closed glass cylinder containing the liquid. The coalescence times of single bubbles contacting the meniscus were monitored using a high speed camera. Results clearly show that stability against coalescence of colliding air bubbles is influenced by both the salt concentration and the approach speed of the bubbles. Contrary to the widespread belief that bubbles in pure water are unstable, we demonstrate that bubbles formed in highly purified water and colliding with the meniscus at very slow approach speeds can survive for minutes or even hours. At higher speeds, bubbles in water only survive for a few seconds, and at still higher speeds they coalesce instantly. Addition of a simple electrolyte (KCl) removes the low-speed stability and shifts the transition between transient stability and instant coalescence to higher approach speeds. At high electrolyte concentration no bubbles were observed to coalesce instantly. These observations are consistent with recent results of Yaminsky et al. (Langmuir 26 (2010) 8061) and the transitions between different regions of behavior are in semi-quantitative agreement with Yaminsky's model. Copyright © 2010 Elsevier Inc. All rights reserved.

Numerical study of a high-speed miniature centrifugal compressor

NASA Astrophysics Data System (ADS)

Li, Xiaoyi

A miniature centrifugal compressor is a key component of reverse Brayton cycle cryogenic cooling system. The system is commonly used to generate a low cryogenic temperature environment for electronics to increase their efficiency, or generate, store and transport cryogenic liquids, such as liquid hydrogen and oxygen, where space limit is also an issue. Because of space limitation, the compressor is composed of a radial IGV, a radial impeller and an axial-direction diffuser (which reduces the radial size because of smaller diameter). As a result of reduction in size, rotating speed of the impeller is as high as 313,000 rpm, and Helium is used as the working fluid, in order to obtain the required static pressure ratio/rise. Two main characteristics of the compressor---miniature and high-speed, make it distinct from conventional compressors. Higher compressor efficiency is required to obtain a higher COP (coefficient of performance) system. Even though miniature centrifugal compressors start to draw researchers' attention in recent years, understanding of the performance and loss mechanism is still lacking. Since current experimental techniques are not advanced enough to capture details of flow at miniature scale, numerical methods dominate miniature turbomachinery study. This work numerically studied a high speed miniature centrifugal compressor with commercial CFD code. The overall performance of the compressor was predicted with consideration of interaction between blade rows by using sliding mesh model. The law of similarity of turbomachinery was validated for small scale machines. It was found that the specific ratio effect needs to be considered when similarity law is applied. But Reynolds number effect can be neglected. The loss mechanism of each component was analyzed. Loss due to turning bend was significant in each component. Tip leakage loss of small scale turbomachines has more impact on the impeller performance than that of large scale ones. Because the splitter was located at downstream of the impeller leading edge, any incidence at the impeller leading edge could deteriorate the splitter performance. Therefore, the impeller with twenty blades had, higher isentropic efficiency than the impeller with ten blades and ten splitters. Based on numerical study, a four-row vaned diffuser replaced a two-row vaned diffuser. It was found that the four-row vaned diffuser had much higher pressure recovery coefficient than the two-row vaned diffuser. However, most of pressure numerically is found to be recovered at the first two rows of diffuser vanes. Consequently, the following suggestions were given to further improve the performance of the miniature centrifugal compressor. (1) Redesign inlet guide vane based on the numerical simulation and experimental results. (2) Add de-swirl vanes in front of the diffuser and before the bend. (3) Replace the current impeller with a twenty-blade impeller. (4) Remove the last two rows of diffuser.

Examination of media coverage of increasing the speed limit to 65 mph

DOT National Transportation Integrated Search

1988-09-01

Heightened newspaper and television coverage of the proposed 65 mph limit may have encouraged increased travel speeds which in turn could have produced an increase in fatalities prior to passage of the national legislation. To pursue this further, NH...

Effects of raising and lowering speed limits on selected roadway sections

DOT National Transportation Integrated Search

1997-01-01

The objective of this research was to examine the effects of raising and lowering posted speed limits on driver behavior for urban and rural nonlimited access highways. Sites selected for study were furnished by the participating States. The study wa...

14 CFR 25.1511 - Flap extended speed.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Flap extended speed. 25.1511 Section 25.1511 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... Limitations § 25.1511 Flap extended speed. The established flap extended speed V FE must be established so...

14 CFR 25.1511 - Flap extended speed.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Flap extended speed. 25.1511 Section 25.1511 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... Limitations § 25.1511 Flap extended speed. The established flap extended speed V FE must be established so...

14 CFR 25.1511 - Flap extended speed.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Flap extended speed. 25.1511 Section 25.1511 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... Limitations § 25.1511 Flap extended speed. The established flap extended speed V FE must be established so...

Advanced Technology Blade testing on the XV-15 Tilt Rotor Research Aircraft

NASA Technical Reports Server (NTRS)

Wellman, Brent

1992-01-01

The XV-15 Tilt Rotor Research Aircraft has just completed the first series of flight tests with the Advanced Technology Blade (ATB) rotor system. The ATB are designed specifically for flight research and provide the ability to alter blade sweep and tip shape. A number of problems were encountered from first installation through envelope expansion to airplane mode flight that required innovative solutions to establish a suitable flight envelope. Prior to operation, the blade retention hardware had to be requalified to a higher rated centrifugal load, because the blade weight was higher than expected. Early flights in the helicopter mode revealed unacceptably high vibratory control system loads which required a temporary modification of the rotor controls to achieve higher speed flight and conversion to airplane mode. The airspeed in airplane mode was limited, however, because of large static control loads. Furthermore, analyses based on refined ATB blade mass and inertia properties indicated a previously unknown high-speed blade mode instability, also requiring airplane-mode maximum airspeed to be restricted. Most recently, a structural failure of an ATB cuff (root fairing) assembly retention structure required a redesign of the assembly. All problems have been addressed and satisfactory solutions have been found to allow continued productive flight research of the emerging tilt rotor concept.

Range Performance of Bombers Powered by Turbine-Propeller Power Plants

NASA Technical Reports Server (NTRS)

Cline, Charles W.

1950-01-01

Calculations have been made to find range? attainable by bombers of gross weights from l40,000 to 300,000 pounds powered by turbine-propeller power plants. Only conventional configurations were considered and emphasis was placed upon using data for structural and aerodynamic characteristics which are typical of modern military airplanes. An effort was made to limit the various parameters invoked in the airplane configuration to practical values. Therefore, extremely high wing loadings, large amounts of sweepback, and very high aspect ratios have not been considered. Power-plant performance was based upon the performance of a typical turbine-propeller engine equipped with propellers designed to maintain high efficiencies at high-subsonic speeds. Results indicated, in general, that the greatest range, for a given gross weight, is obtained by airplanes of high wing loading, unless the higher cruising speeds associated with the high-wing-loading airplanes require-the use of thinner wing sections. Further results showed the effect of cruising at-high speeds, of operation at very high altitudes, and of carrying large bomb loads.

Speed-accuracy trade-off in skilled typewriting: decomposing the contributions of hierarchical control loops.

PubMed

Yamaguchi, Motonori; Crump, Matthew J C; Logan, Gordon D

2013-06-01

Typing performance involves hierarchically structured control systems: At the higher level, an outer loop generates a word or a series of words to be typed; at the lower level, an inner loop activates the keystrokes comprising the word in parallel and executes them in the correct order. The present experiments examined contributions of the outer- and inner-loop processes to the control of speed and accuracy in typewriting. Experiments 1 and 2 involved discontinuous typing of single words, and Experiments 3 and 4 involved continuous typing of paragraphs. Across experiments, typists were able to trade speed for accuracy but were unable to type at rates faster than 100 ms/keystroke, implying limits to the flexibility of the underlying processes. The analyses of the component latencies and errors indicated that the majority of the trade-offs were due to inner-loop processing. The contribution of outer-loop processing to the trade-offs was small, but it resulted in large costs in error rate. Implications for strategic control of automatic processes are discussed. (PsycINFO Database Record (c) 2013 APA, all rights reserved).

Imaging initial formation processes of nanobubbles at the graphite-water interface through high-speed atomic force microscopy

NASA Astrophysics Data System (ADS)

Liao, Hsien-Shun; Yang, Chih-Wen; Ko, Hsien-Chen; Hwu, En-Te; Hwang, Ing-Shouh

2018-03-01

The initial formation process of nanobubbles at solid-water interfaces remains unclear because of the limitations of current imaging techniques. To directly observe the formation process, an astigmatic high-speed atomic force microscope (AFM) was modified to enable imaging in the liquid environment. By using a customized cantilever holder, the resonance of small cantilevers was effectively enhanced in water. The proposed high-speed imaging technique yielded highly dynamic quasi-two-dimensional (2D) gas structures (thickness: 20-30 nm) initially at the graphite-water interface. The 2D structures were laterally mobile mainly within certain areas, but occasionally a gas structure might extensively migrate and settle in a new area. The 2D structures were often confined by substrate step edges in one lateral dimension. Eventually, all quasi-2D gas structures were transformed into cap-shaped nanobubbles of higher heights and reduced lateral dimensions. These nanobubbles were immobile and remained stable under continuous AFM imaging. This study demonstrated that nanobubbles could be stably imaged at a scan rate of 100 lines per second (640 μm/s).

Resonant Scanning with Large Field of View Reduces Photobleaching and Enhances Fluorescence Yield in STED Microscopy.

PubMed

Wu, Yong; Wu, Xundong; Lu, Rong; Zhang, Jin; Toro, Ligia; Stefani, Enrico

2015-10-01

Photobleaching is a major limitation of superresolution Stimulated Depletion Emission (STED) microscopy. Fast scanning has long been considered an effective means to reduce photobleaching in fluorescence microscopy, but a careful quantitative study of this issue is missing. In this paper, we show that the photobleaching rate in STED microscopy can be slowed down and the fluorescence yield be enhanced by scanning with high speed, enabled by using large field of view in a custom-built resonant-scanning STED microscope. The effect of scanning speed on photobleaching and fluorescence yield is more remarkable at higher levels of depletion laser irradiance, and virtually disappears in conventional confocal microscopy. With ≥6 GW∙cm(-2) depletion irradiance, we were able to extend the fluorophore survival time of Atto 647N and Abberior STAR 635P by ~80% with 8-fold wider field of view. We confirm that STED Photobleaching is primarily caused by the depletion light acting upon the excited fluorophores. Experimental data agree with a theoretical model. Our results encourage further increasing the linear scanning speed for photobleaching reduction in STED microscopy.

Large grain instruction and phonological awareness skill influence rime sensitivity, processing speed, and early decoding skill in adult L2 learners

PubMed Central

Brennan, Christine; Booth, James R.

2016-01-01

Linguistic knowledge, cognitive ability, and instruction influence how adults acquire a second orthography yet it remains unclear how different forms of instruction influence grain size sensitivity and subsequent decoding skill and speed. Thirty-seven monolingual, literate English-speaking adults were trained on a novel artificial orthography given initial instruction that directed attention to either large or small grain size units (i.e., words or letters). We examined how initial instruction influenced processing speed (i.e., reaction time (RT)) and sensitivity to different orthographic grain sizes (i.e., rimes and letters). Directing attention to large grain size units during initial instruction resulted in higher accuracy for rimes, whereas directing attention to smaller grain size units resulted in slower RTs across all measures. Additionally, phonological awareness skill modulated early learning effects, compensating for the limitations of the initial instruction provided. Collectively, these findings suggest that when adults are learning to read a second orthography, consideration should be given to how initial instruction directs attention to different grain sizes and inherent phonological awareness ability. PMID:27829705

Bearing fatigue investigation 3

NASA Technical Reports Server (NTRS)

Nahm, A. H.; Bamberger, E. N.; Signer, H. R.

1982-01-01

The operating characteristics of large diameter rolling-element bearings in the ultra high speed regimes expected in advanced turbine engines for high performance aircraft were investigated. A high temperature lubricant, DuPont Krytox 143 AC, was evaluated at bearing speeds to 3 million DN. Compared to the results of earlier, similar tests using a MIL-L-23699 (Type II) lubricant, bearings lubricated with the high density Krytox fluid showed significantly higher power requirements. Additionally, short bearing lives were observed when this fluid was used with AISI M50 bearings in an air atmosphere. The primary mode of failure was corrosion initiated surface distress (fatigue) on the raceways. The potential of a case-carburized bearing to sustain a combination of high-tangential and hertzian stresses without experiencing race fracture was also investigated. Limited full scale bearing tests of a 120 mm bore ball bearing at a speed of 25,000 rpm (3 million DN) indicated that a carburized material could sustain spalling fatigue without subsequent propagation to fracture. Planned life tests of the carburized material had to be aborted, however, because of apparent processing-induced material defects.

Wildlife-vehicle collisions in Lanzarote Biosphere Reserve, Canary Islands.

PubMed

Tejera, Gustavo; Rodríguez, Beneharo; Armas, Carlos; Rodríguez, Airam

2018-01-01

Insular wildlife is more prone to extinction than their mainland relatives. Thus, a basic understanding of non-natural mortality sources is the first step in the development of conservation management plans. The Canary Islands are an important tourist destination due to their unique climate and rich scenery and biodiversity. During the last few decades, there has been significant development of urban areas and busy road networks. However, there have been no studies describing the effects of road mortality on wildlife in this archipelago. We describe the temporal and spatial patterns of wildlife roadkill in Lanzarote (UNESCO Biosphere Reserve), using counts from cars for an entire annual cycle. A total of 666 roadkills were recorded (monthly average of 0.09 birds/km and 0.14 mammals/km) comprising at least 37 species including native birds and introduced mammals. Seasonal abundance, richness and diversity of roadkills showed a high peak during summer months for both mammals and birds. GLMs indicated that accidents (including birds and mammals) have a higher probability of occurrence close to houses and on roads with high speed limits. When analysed separately, mammal kills occurred in sectors with high speed limits, close to houses and in areas surrounded by exotic bushes, while bird roadkills appeared in road sectors with high speed limits, close to houses and low traffic volume. Our findings highlight that roads are a potential threat to native birds in the eastern Canary Islands. Detailed studies on the local population dynamics of highly affected species, such as the Houbara Bustard, Eurasian Stone Curlew, Barn Owl or Southern Shrike, are urgently needed to determine whether these levels of road mortality are sustainable.

Wildlife-vehicle collisions in Lanzarote Biosphere Reserve, Canary Islands

PubMed Central

Tejera, Gustavo; Armas, Carlos; Rodríguez, Airam

2018-01-01

Insular wildlife is more prone to extinction than their mainland relatives. Thus, a basic understanding of non-natural mortality sources is the first step in the development of conservation management plans. The Canary Islands are an important tourist destination due to their unique climate and rich scenery and biodiversity. During the last few decades, there has been significant development of urban areas and busy road networks. However, there have been no studies describing the effects of road mortality on wildlife in this archipelago. We describe the temporal and spatial patterns of wildlife roadkill in Lanzarote (UNESCO Biosphere Reserve), using counts from cars for an entire annual cycle. A total of 666 roadkills were recorded (monthly average of 0.09 birds/km and 0.14 mammals/km) comprising at least 37 species including native birds and introduced mammals. Seasonal abundance, richness and diversity of roadkills showed a high peak during summer months for both mammals and birds. GLMs indicated that accidents (including birds and mammals) have a higher probability of occurrence close to houses and on roads with high speed limits. When analysed separately, mammal kills occurred in sectors with high speed limits, close to houses and in areas surrounded by exotic bushes, while bird roadkills appeared in road sectors with high speed limits, close to houses and low traffic volume. Our findings highlight that roads are a potential threat to native birds in the eastern Canary Islands. Detailed studies on the local population dynamics of highly affected species, such as the Houbara Bustard, Eurasian Stone Curlew, Barn Owl or Southern Shrike, are urgently needed to determine whether these levels of road mortality are sustainable. PMID:29561864

Modeling and analyzing traffic safety perceptions: An application to the speed limit reduction pilot project in Edmonton, Alberta.

PubMed

El-Basyouny, Karim; El-Bassiouni, Mohamed Yahia

2013-03-01

To address the speeding problem in residential areas, the City of Edmonton initiated a pilot project to reduce the posted speed limit from 50km/h to 40km/h within six residential communities. This paper investigates the community perceptions of traffic safety within the six pilot communities in two phases: prior to project initiation (pre-pilot) and following the end of the project (post-pilot). This objective was accomplished by analyzing the results of two random dialing telephone surveys comprising 300 residents each. A preliminary analysis showed compatible demographic configurations for the two samples and confirmed that the residents were aware of both the posted speed limits and the adopted speed management controls. For the confirmatory factor analysis (CFA), a two-group (pre-pilot and post-pilot) three-factor model was used to assess the residents' perceptions of the speeding behavior (Speeding), their concerns about traffic safety issues (Concerns), and their perceptions of traffic safety (Safety). Comparing the CFA results of the post-pilot survey versus those of the pre-pilot survey, it was evident that there was a significant decrease in Speeding and Concerns accompanied by a significant increase in Safety. A structural equations model (SEM) was also fitted to the data in order to assess the impact of Speeding and Concerns on Safety. The results showed that Concerns increase significantly with Speeding, and that both factors have significant negative impacts on Safety. However, while the impact of Concerns on Safety was direct, that of Speeding on Safety was largely indirect (i.e., mediated through Concerns). Overall, the multivariate analysis has demonstrated that the pilot project was successful in improving the residents' perceptions of traffic safety in their community. Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.

Exponential increase in the on-off ratio of conductance in organic memory devices by controlling the surface morphology of the devices

NASA Astrophysics Data System (ADS)

Vyas, Giriraj; Dagar, Parveen; Sahu, Satyajit

2018-05-01

We have shown an exponential increase in the ratio of conductance in the on and off states of switching devices by controlling the surface morphology of the thin films for the device by depositing at different rotational speeds. The pinholes which are preferred topography on the surface at higher rotational speed give rise to higher on-off ratio of current from the devices fabricated at the speed. The lower rotational speed contributes to higher thickness of the film and hence no switching. For thicker films, the domain is formed due to phase segregation between the two components in the film, which also indicates that the film is far from thermal equilibrium. At higher speed, there is very little scope of segregation when the film is drying up. Hence, there are only few pinholes on the surface of the film which are shallow. So, the filamentary mechanism of switching in memory devices can be firmly established by varying the speed of thin film deposition which leads to phase segregation of the materials. Thus, the formation of filament can be regulated by controlling the thickness and the surface morphology.

Use of electromyogram telemetry to assess swimming activity of adult spring Chinook salmon migrating past a Columbia River dam

USGS Publications Warehouse

Brown, R.S.; Geist, D.R.; Mesa, M.G.

2006-01-01

Electromyogram (EMG) radiotelemetry was used to estimate the swim speeds of spring Chinook salmon Oncorhynchus tshawytscha migrating upstream past a Columbia River dam. Electrodes from EMG transmitters were surgically implanted in the red muscle of fish captured at Bonneville Dam, and output from the tags was calibrated to defined swim speeds for each fish in a tunnel respirometer. The fish were then released below Bonneville Dam and radio-tracked as they migrated through the tailraces, fishways, and forebays of the dam. On average, swim speed was significantly higher when tagged salmon were moving through tailraces than when they were moving through other parts of the dam. Specifically, swim speeds for fish in tailraces (106.4 cm/s) were 23% higher than those of fish in fishways (84.9 cm/s) and 32% higher than those of fish in forebays (80.2 cm/s). Swim speeds were higher in fishways during the day than during the night, but there were no diel differences in swim speeds in tailraces and forebays. During dam passage, Chinook salmon spent the most time in tailraces, followed by fishways and forebays. ?? Copyright by the American Fisheries Society 2006.

The metabolic, locomotor and sex-dependent effects of elevated temperature on Trinidadian guppies: limited capacity for acclimation.

PubMed

Muñoz, Nicolas J; Breckels, Ross D; Neff, Bryan D

2012-10-01

Global warming poses a threat to many ectothermic organisms because of the harmful effects that elevated temperatures can have on resting metabolic rate (RMR) and body size. This study evaluated the thermal sensitivity of Trinidadian guppies (Poecilia reticulata) by describing the effects of developmental temperature on mass, burst speed and RMR, and investigated whether these tropical fish can developmentally acclimate to their thermal conditions. These traits were measured following exposure to one of three treatments: 70 days at 23, 25, 28 or 30°C (acclimated groups); 6 h at 23, 28 or 30°C following 70 days at 25°C (unacclimated groups); or 6 h at 25°C following 70 days in another 25°C tank (control group). Body mass was lower in warmer temperatures, particularly amongst females and individuals reared at 30°C. The burst speed of fish acclimated to each temperature did not differ and was marginally higher than that of unacclimated fish, indicative of complete compensation. Conversely, acclimated and unacclimated fish did not differ in their RMR at each temperature. Amongst the acclimated groups, RMR was significantly higher at 30°C, indicating that guppies may become thermally limited at this temperature as a result of less energy being available for growth, reproduction and locomotion. Like other tropical ectotherms, guppies appear to be unable to adjust their RMR through physiological acclimation and may consequently be susceptible to rising temperatures. Also, because larger females have higher fecundity, our data suggest that fecundity will be reduced in a warmer climate, potentially decreasing the viability of guppy populations.

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

Diaz, Ivan; Verdun, Francis R.; Bochud, François O., E-mail: francois.bochud@chuv.ch

Purpose: Signal detection on 3D medical images depends on many factors, such as foveal and peripheral vision, the type of signal, and background complexity, and the speed at which the frames are displayed. In this paper, the authors focus on the speed with which radiologists and naïve observers search through medical images. Prior to the study, the authors asked the radiologists to estimate the speed at which they scrolled through CT sets. They gave a subjective estimate of 5 frames per second (fps). The aim of this paper is to measure and analyze the speed with which humans scroll throughmore » image stacks, showing a method to visually display the behavior of observers as the search is made as well as measuring the accuracy of the decisions. This information will be useful in the development of model observers, mathematical algorithms that can be used to evaluate diagnostic imaging systems. Methods: The authors performed a series of 3D 4-alternative forced-choice lung nodule detection tasks on volumetric stacks of chest CT images iteratively reconstructed in lung algorithm. The strategy used by three radiologists and three naïve observers was assessed using an eye-tracker in order to establish where their gaze was fixed during the experiment and to verify that when a decision was made, a correct answer was not due only to chance. In a first set of experiments, the observers were restricted to read the images at three fixed speeds of image scrolling and were allowed to see each alternative once. In the second set of experiments, the subjects were allowed to scroll through the image stacks at will with no time or gaze limits. In both static-speed and free-scrolling conditions, the four image stacks were displayed simultaneously. All trials were shown at two different image contrasts. Results: The authors were able to determine a histogram of scrolling speeds in frames per second. The scrolling speed of the naïve observers and the radiologists at the moment the signal was detected was measured at 25–30 fps. For the task chosen, the performance of the observers was not affected by the contrast or experience of the observer. However, the naïve observers exhibited a different pattern of scrolling than the radiologists, which included a tendency toward higher number of direction changes and number of slices viewed. Conclusions: The authors have determined a distribution of speeds for volumetric detection tasks. The speed at detection was higher than that subjectively estimated by the radiologists before the experiment. The speed information that was measured will be useful in the development of 3D model observers, especially anthropomorphic model observers which try to mimic human behavior.« less

Stratospheric turbulence measurements and models for aerospace plane design

NASA Technical Reports Server (NTRS)

Ehernberger, L. J.

1992-01-01

Progress in computational atmospheric dynamics is exhibiting the ability of numerical simulation to describe instability processes associated with turbulence observed at altitudes between 15 and 25 km in the lower stratosphere. As these numerical simulation tools mature, they can be used to extend estimates of atmospheric perturbations from the present gust database for airplane design at altitudes below 15 km to altitudes between 25 and 50 km where aerospace plane operation would be at hypersonic speeds. The amount of available gust data and number of temperature perturbation observations are limited at altitudes between 15 and 25 km. On the other hand, in-situ gust data at higher altitudes are virtually nonexistent. The uncertain potential for future airbreathing hypersonic flight research vehicles to encounter strong turbulence at higher altitudes could penalize the design of these vehicles by undue cost or limitations on performance. Because the atmospheric structure changes markedly with altitude, direct extrapolation of gust magnitudes and encounter probabilities to the higher flight altitudes is not advisable. This paper presents a brief review of turbulence characteristics observed in the lower stratosphere and highlights the progress of computational atmospheric dynamics that may be used to estimate the severity of atmospheric transients at higher altitudes.

Human Kinematics of Cochlear Implant Surgery: An Investigation of Insertion Micro-Motions and Speed Limitations.

PubMed

Kesler, Kyle; Dillon, Neal P; Fichera, Loris; Labadie, Robert F

2017-09-01

Objectives Document human motions associated with cochlear implant electrode insertion at different speeds and determine the lower limit of continuous insertion speed by a human. Study Design Observational. Setting Academic medical center. Subjects and Methods Cochlear implant forceps were coupled to a frame containing reflective fiducials, which enabled optical tracking of the forceps' tip position in real time. Otolaryngologists (n = 14) performed mock electrode insertions at different speeds based on recommendations from the literature: "fast" (96 mm/min), "stable" (as slow as possible without stopping), and "slow" (15 mm/min). For each insertion, the following metrics were calculated from the tracked position data: percentage of time at prescribed speed, percentage of time the surgeon stopped moving forward, and number of direction reversals (ie, going from forward to backward motion). Results Fast insertion trials resulted in better adherence to the prescribed speed (45.4% of the overall time), no motion interruptions, and no reversals, as compared with slow insertions (18.6% of time at prescribed speed, 15.7% stopped time, and an average of 18.6 reversals per trial). These differences were statistically significant for all metrics ( P < .01). The metrics for the fast and stable insertions were comparable; however, stable insertions were performed 44% slower on average. The mean stable insertion speed was 52 ± 19.3 mm/min. Conclusion Results indicate that continuous insertion of a cochlear implant electrode at 15 mm/min is not feasible for human operators. The lower limit of continuous forward insertion is 52 mm/min on average. Guidelines on manual insertion kinematics should consider this practical limit of human motion.

14 CFR 25.1513 - Minimum control speed.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Minimum control speed. 25.1513 Section 25.1513 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... Limitations § 25.1513 Minimum control speed. The minimum control speed V MC determined under § 25.149 must be...

14 CFR 25.1513 - Minimum control speed.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Minimum control speed. 25.1513 Section 25.1513 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... Limitations § 25.1513 Minimum control speed. The minimum control speed V MC determined under § 25.149 must be...

The impact of the 65 mph speed limit on Virginia's rural interstate highways through 1989.

DOT National Transportation Integrated Search

1990-01-01

In April 1987, Congress passed the Surface Transportation and Uniform Relocation Assistance Act (STURAA) which permitted states to raise their maximum speed limit on rural interstate highways (rural interstates) to 65 mph. Since then, 40 states, incl...

Partial body weight support treadmill training speed influences paretic and non-paretic leg muscle activation, stride characteristics, and ratings of perceived exertion during acute stroke rehabilitation.

PubMed

Burnfield, Judith M; Buster, Thad W; Goldman, Amy J; Corbridge, Laura M; Harper-Hanigan, Kellee

2016-06-01

Intensive task-specific training is promoted as one approach for facilitating neural plastic brain changes and associated motor behavior gains following neurologic injury. Partial body weight support treadmill training (PBWSTT), is one task-specific approach frequently used to improve walking during the acute period of stroke recovery (<1month post infarct). However, only limited data have been published regarding the relationship between training parameters and physiologic demands during this early recovery phase. To examine the impact of four walking speeds on stride characteristics, lower extremity muscle demands (both paretic and non-paretic), Borg ratings of perceived exertion (RPE), and blood pressure. A prospective, repeated measures design was used. Ten inpatients post unilateral stroke participated. Following three familiarization sessions, participants engaged in PBWSTT at four predetermined speeds (0.5, 1.0, 1.5 and 2.0mph) while bilateral electromyographic and stride characteristic data were recorded. RPE was evaluated immediately following each trial. Stride length, cadence, and paretic single limb support increased with faster walking speeds (p⩽0.001), while non-paretic single limb support remained nearly constant. Faster walking resulted in greater peak and mean muscle activation in the paretic medial hamstrings, vastus lateralis and medial gastrocnemius, and non-paretic medial gastrocnemius (p⩽0.001). RPE also was greatest at the fastest compared to two slowest speeds (p<0.05). During the acute phase of stroke recovery, PBWSTT at the fastest speed (2.0mph) promoted practice of a more optimal gait pattern with greater intensity of effort as evidenced by the longer stride length, increased between-limb symmetry, greater muscle activation, and higher RPE compared to training at the slowest speeds. Copyright © 2016 Elsevier B.V. All rights reserved.

Extending the Constant Power Speed Range of the Brushless DC Motor through Dual Mode Inverter Control -- Part II: Laboratory Proof-of-Principle

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

Lawler, J.S.

2001-10-29

Previous theoretical work has shown that when all loss mechanisms are neglected the constant power speed range (CPSR) of a brushless dc motor (BDCM) is infinite when the motor is driven by the dual-mode inverter control (DMIC) [1,2]. In a physical drive, losses, particularly speed-sensitive losses, will limit the CPSR to a finite value. In this paper we report the results of laboratory testing of a low-inductance, 7.5-hp BDCM driven by the DMIC. The speed rating of the test motor rotor limited the upper speed of the testing, and the results show that the CPSR of the test machine ismore » greater than 6:1 when driven by the DMIC. Current wave shape, peak, and rms values remained controlled and within rating over the entire speed range. The laboratory measurements allowed the speed-sensitive losses to be quantified and incorporated into computer simulation models, which then accurately reproduce the results of lab testing. The simulator shows that the limiting CPSR of the test motor is 8:1. These results confirm that the DMIC is capable of driving low-inductance BDCMs over the wide CPSR that would be required in electric vehicle applications.« less

Solving the aerodynamics of fungal flight: How air viscosity slows spore motion

PubMed Central

Fischer, Mark W. F.; Stolze-Rybczynski, Jessica L.; Davis, Diana J.; Cui, Yunluan; Money, Nicholas P.

2010-01-01

Viscous drag causes the rapid deceleration of fungal spores after high-speed launches and limits discharge distance. Stokes' law posits a linear relationship between drag force and velocity. It provides an excellent fit to experimental measurements of the terminal velocity of free-falling spores and other instances of low Reynolds number motion (Re<1). More complex, non-linear drag models have been devised for movements characterized by higher Re, but their effectiveness for modeling the launch of fast-moving fungal spores has not been tested. In this paper, we use data on spore discharge processes obtained from ultra-high-speed video recordings to evaluate the effects of air viscosity predicted by Stokes' law and a commonly used non-linear drag model. We find that discharge distances predicted from launch speeds by Stokes' model provide a much better match to measured distances than estimates from the more complex drag model. Stokes' model works better over a wide range projectile sizes, launch speeds, and discharge distances, from microscopic mushroom ballistospores discharged at <1 m/s over a distance of <0.1 mm (Re<1.0), to macroscopic sporangia of Pilobolus that are launched at >10 m/s and travel as far as 2.5 m (Re>100). PMID:21036338

Wear-Induced Changes in FSW Tool Pin Profile: Effect of Process Parameters

NASA Astrophysics Data System (ADS)

Sahlot, Pankaj; Jha, Kaushal; Dey, G. K.; Arora, Amit

2018-06-01

Friction stir welding (FSW) of high melting point metallic (HMPM) materials has limited application due to tool wear and relatively short tool life. Tool wear changes the profile of the tool pin and adversely affects weld properties. A quantitative understanding of tool wear and tool pin profile is crucial to develop the process for joining of HMPM materials. Here we present a quantitative wear study of H13 steel tool pin profile for FSW of CuCrZr alloy. The tool pin profile is analyzed at multiple traverse distances for welding with various tool rotational and traverse speeds. The results indicate that measured wear depth is small near the pin root and significantly increases towards the tip. Near the pin tip, wear depth increases with increase in tool rotational speed. However, change in wear depth near the pin root is minimal. Wear depth also increases with decrease in tool traverse speeds. Tool pin wear from the bottom results in pin length reduction, which is greater for higher tool rotational speeds, and longer traverse distances. The pin profile changes due to wear and result in root defect for long traverse distance. This quantitative understanding of tool wear would be helpful to estimate tool wear, optimize process parameters, and tool pin shape during FSW of HMPM materials.

Effectiveness of voluntary conservation agreements: case study of endangered whales and commercial whale watching.

PubMed

Wiley, David N; Moller, Just C; Pace, Richard M; Carlson, Carole

2008-04-01

The use of voluntary approaches to achieve conservation goals is becoming increasingly popular. Nevertheless, few researchers have quantitatively evaluated their efficacy. In 1998 industry, government agencies, and nongovernmental organizations established a voluntary conservation program for whale watching in the northeast region of the United States, with the intent to avoid collisions with and harassment of endangered whales by commercial and recreational whale-watching vessels. One important aspect of the program was the establishment of 3 speed zones within specific distances of whales. We wanted to determine the level of compliance with this aspect of the program to gauge its efficacy and gain insights into the effectiveness of voluntary measures as a conservation tool. Inconspicuous observers accompanied 46 commercial whale-watching trips from 12 companies in 2003 (n= 35) and 2004 (n= 11). During each trip, vessel position and speed were collected at 5-second intervals with a GPS receiver. Binoculars with internal laser rangefinders and digital compasses were used to record range and bearing to sighted whales. We mapped whale locations with ArcGIS. We created speed-zone buffers around sighted whales and overlaid them with vessel-track and speed data to evaluate compliance. Speeds in excess of those recommended by the program were considered noncompliant. We judged the magnitude of noncompliance by comparing a vessel's maximum speed within a zone to its maximum recorded trip speed. The level of noncompliance was high (mean 0.78; company range 0.74-0.88), some companies were more compliant than others (p= 0.02), noncompliance was significantly higher in zones farther from whales (p < 0.001), and operators approached the maximum speed capabilities of their vessel in all zones. The voluntary conservation program did not achieve the goal of substantially limiting vessel speed near whales. Our results support the need for conservation programs to have quantifiable metrics and frequent evaluation to ensure efficacy.

Atmospheric Ionizing Radiation and the High Speed Civil Transport. Chapter 1

NASA Technical Reports Server (NTRS)

Maiden, D. L.; Wilson, J. W.; Jones, I. W.; Goldhagen, P.

2003-01-01

Atmospheric ionizing radiation is produced by extraterrestrial radiations incident on the Earth's atmosphere. These extraterrestrial radiations are of two sources: ever present galactic cosmic rays with origin outside the solar system and transient solar particle events that are at times very intense events associated with solar activity lasting several hours to a few days. Although the galactic radiation penetrating through the atmosphere to the ground is low in intensity, the intensity is more than two orders of magnitude greater at commercial aircraft altitudes. The radiation levels at the higher altitudes of the High Speed Civil Transport (HSCT) are an additional factor of two higher. Ionizing radiation produces chemically active radicals in biological tissues that alter the cell function or result in cell death. Protection standards against low levels of ionizing radiation are based on limitation of excess cancer mortality or limitation of developmental injury resulting in permanent damage to the offspring during pregnancy. The crews of commercial air transport operations are considered as radiation workers by the EPA, the FAA, and the International Commission on Radiological Protection (ICRP). The annual exposures of aircrews depend on the latitudes and altitudes of operation and flight time. Flight hours have significantly increased since deregulation of the airline industry in the 1980's. The FAA estimates annual subsonic aircrew exposures to range from 0.2 to 9.1 mSv compared to 0.5 mSv exposure of the average nuclear power plant worker in the nuclear industry. The commercial aircrews of the HSCT may receive exposures above recently recommended allowable limits for even radiation workers if flying their allowable number of flight hours. An adequate protection philosophy for background exposures in HSCT commercial airtraffic cannot be developed at this time due to current uncertainty in environmental levels. In addition, if a large solar particle event occurs during flight at HSCT altitudes then passengers and crew may greatly exceed allowable limits unless means are available to reduce exposures.

The Relationship between Multiplication Fact Speed-Recall and Fluency and Higher Level Mathematics Learning with Eighth Grade Middle School Students

ERIC Educational Resources Information Center

Curry, Steven James

2012-01-01

This quantitative study investigated relationships between higher level mathematics learning and multiplication fact fluency, multiplication fact speed-recall, and reading grade equivalency of eighth grade students in Algebra I and Pre-Algebra. Higher level mathematics learning was indicated by an average score of 80% or higher on first and second…

Predator-induced morphology enhances escape locomotion in crucian carp.

PubMed

Domenici, Paolo; Turesson, Håkan; Brodersen, Jakob; Brönmark, Christer

2008-01-22

Fishes show a remarkable diversity of shapes which have been associated with their swimming abilities and anti-predator adaptations. The crucian carp (Carassius carassius) provides an extreme example of phenotypic plasticity in body shape which makes it a unique model organism for evaluating the relationship between body form and function in fishes. In crucian carp, a deep body is induced by the presence of pike (Esox lucius), and this results in lower vulnerability to gape-limited predators, such as pike itself. Here, we demonstrate that deep-bodied crucian carp attain higher speed, acceleration and turning rate during anti-predator responses than shallow-bodied crucian carp. Therefore, a predator-induced morphology in crucian carp enhances their escape locomotor performance. The deep-bodied carp also show higher percentage of muscle mass. Therefore, their superior performance in escape swimming may be due to a combination of higher muscle power and higher thrust.

Energy efficiency : potential fuel savings generated by a national speed limit would be influenced by many other factors.

DOT National Transportation Integrated Search

2008-11-07

"Congress expressed interest in obtaining information on using a national speed limit to reduce fuel consumption. In response to the request, we reviewed existing literature and consulted knowledgeable stakeholders on the following: (1) What is the r...

Evaluation of variable speed limits on I-270/I-255 in St. Louis.

DOT National Transportation Integrated Search

2010-10-01

In May of 2008, MoDOT installed a Variable Speed Limit (VSL) system along the I270/I255 corridor in St. Louis. This project evaluated the VSL system and its potential impacts and benefits to the transportation users. The technical system ...

An investigation of issues related to raising the rural interstate speed limit in Virginia.

DOT National Transportation Integrated Search

1988-01-01

In April of 1987, Congress passed the Surface Transportation and Uniform Relocation Assistance Act of 1987, which allows the states to raise, without penalty, the speed limit on interstate highways outside of urbanized areas with a population of 50,0...

14 CFR 23.1583 - Operating limitations.

Code of Federal Regulations, 2010 CFR

2010-01-01

... restrictions on smoking in the airplane. (p) Types of surface. A statement of the types of surface on which... type flight tests, together with recommended entry speeds and any other associated limitations. No... demonstrated in the type flight tests, together with recommended entry speeds and any other associated...

14 CFR 23.1583 - Operating limitations.

Code of Federal Regulations, 2011 CFR

2011-01-01

... restrictions on smoking in the airplane. (p) Types of surface. A statement of the types of surface on which... type flight tests, together with recommended entry speeds and any other associated limitations. No... demonstrated in the type flight tests, together with recommended entry speeds and any other associated...

Radiation Safety Issues in High Altitude Commercial Aircraft

NASA Technical Reports Server (NTRS)

Wilson, John W.; Cucinotta, Francis A.; Shinn, Judy L.

1995-01-01

The development of a global economy makes the outlook for high speed commercial intercontinental flight feasible, and the development of various configurations operating from 20 to 30 km have been proposed. In addition to the still unresolved issues relating to current commercial operations (12-16 km), the higher dose rates associated with the higher operating altitudes makes il imperative that the uncertainties in the atmospheric radiation environment and the associated health risks be re-examined. Atmospheric radiation associated with the galactic cosmic rays forms a background level which may, under some circumstances, exceed newly recommended allowable exposure limits proposed on the basis of recent evaluations of the A -bomb survivor data (due to increased risk coefficients). These larger risk coefficients, within the context of the methodology for estimating exposure limits, are resulting in exceedingly low estimated allowable exposure limits which may impact even present day flight operations and was the reason for the CEC workshop in Luxembourg (1990). At higher operating altitudes, solar particles events can produce exposures many orders of magnitude above background levels and pose significant health risks to the most sensitive individuals (such as during pregnancy). In this case the appropriate quality factors are undefined, and some evidence exists which indicates that the quality factor for stochastic effects is a substantial underestimate.

Summary of state speed laws

DOT National Transportation Integrated Search

2006-04-01

This summary reports only the status of State statutes or regulations that are concerned with either speed limit or speed-related violations. Local laws are not reported. Unless otherwise indicated, the status of the State laws or regulations reporte...

Summary of state speed laws

DOT National Transportation Integrated Search

2007-08-01

This summary reports only the status of State statutes or regulations that are concerned with either speed limit or speed-related violations. Local laws are not reported. Unless otherwise indicated, the status of the State laws or regulations reporte...

Maximal metabolic rates during voluntary exercise, forced exercise, and cold exposure in house mice selectively bred for high wheel-running.

PubMed

Rezende, Enrico L; Chappell, Mark A; Gomes, Fernando R; Malisch, Jessica L; Garland, Theodore

2005-06-01

Selective breeding for high wheel-running activity has generated four lines of laboratory house mice (S lines) that run about 170% more than their control counterparts (C lines) on a daily basis, mostly because they run faster. We tested whether maximum aerobic metabolic rates (V(O2max)) have evolved in concert with wheel-running, using 48 females from generation 35. Voluntary activity and metabolic rates were measured on days 5+6 of wheel access (mimicking conditions during selection), using wheels enclosed in metabolic chambers. Following this, V(O2max) was measured twice on a motorized treadmill and twice during cold-exposure in a heliox atmosphere (HeO2). Almost all measurements, except heliox V(O2max), were significantly repeatable. After accounting for differences in body mass (S < C) and variation in age at testing, S and C did not differ in V(O2max) during forced exercise or in heliox, nor in maximal running speeds on the treadmill. However, running speeds and V(O2max) during voluntary exercise were significantly higher in S lines. Nevertheless, S mice never voluntarily achieved the V(O2max) elicited during their forced treadmill trials, suggesting that aerobic capacity per se is not limiting the evolution of even higher wheel-running speeds in these lines. Our results support the hypothesis that S mice have genetically higher motivation for wheel-running and they demonstrate that behavior can sometimes evolve independently of performance capacities. We also discuss the possible importance of domestication as a confounding factor to extrapolate results from this animal model to natural populations.

Orbital simulations of laser-propelled spacecraft

NASA Astrophysics Data System (ADS)

Zhang, Qicheng; Lubin, Philip M.; Hughes, Gary B.; Melis, Carl; Walsh, Kevin J.

2015-09-01

Spacecraft accelerate by directing propellant in the opposite direction. In the traditional approach, the propellant is carried on board in the form of material fuel. This approach has the drawback of being limited in Delta v by the amount of fuel launched with the craft, a limit that does not scale well to high Delta v due to the massive nature of the fuel. Directed energy photon propulsion solves this problem by eliminating the need for on-board fuel storage. We discuss our system which uses a phased array of lasers to propel the spacecraft which contributes no mass to the spacecraft beyond that of the reflector, enabling a prolonged acceleration and much higher final speeds. This paper compares the effectiveness of such a system for propelling spacecraft into interplanetary and interstellar space across various laser and sail configurations. Simulated parameters include laser power, optics size and orbit as well as payload mass, reflector size and the trajectory of the spacecraft. As one example, a 70 GW laser with 10 km optics could propel a 1 kg craft past Neptune (~30 au) in 5 days at 4% the speed of light, or a 1 g "wafer-sat" past Mars (~0.5 au) in 20 minutes at 21% the speed of light. However, even lasers down to 2 kW power and 1 m optics show noticeable effect on gram-class payloads, boosting their altitude in low Earth orbits by several kilometers per day which is already sufficient to be of practical use.

77 FR 14346 - Proposed Information Collection; Comment Request; Implementation of Vessel Speed Restrictions To...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-09

... Collection; Comment Request; Implementation of Vessel Speed Restrictions To Reduce the Threat of Ship... implementing speed restrictions to reduce the incidence and severity of ship collisions with North Atlantic... document that a deviation from the 10-knot speed limit was necessary for safe maneuverability under certain...

Effects of automated speed enforcement in Montgomery County, Maryland, on vehicle speeds, public opinion, and crashes.

PubMed

Hu, Wen; McCartt, Anne T

2016-09-01

In May 2007, Montgomery County, Maryland, implemented an automated speed enforcement program, with cameras allowed on residential streets with speed limits of 35 mph or lower and in school zones. In 2009, the state speed camera law increased the enforcement threshold from 11 to 12 mph over the speed limit and restricted school zone enforcement hours. In 2012, the county began using a corridor approach, in which cameras were periodically moved along the length of a roadway segment. The long-term effects of the speed camera program on travel speeds, public attitudes, and crashes were evaluated. Changes in travel speeds at camera sites from 6 months before the program began to 7½ years after were compared with changes in speeds at control sites in the nearby Virginia counties of Fairfax and Arlington. A telephone survey of Montgomery County drivers was conducted in Fall 2014 to examine attitudes and experiences related to automated speed enforcement. Using data on crashes during 2004-2013, logistic regression models examined the program's effects on the likelihood that a crash involved an incapacitating or fatal injury on camera-eligible roads and on potential spillover roads in Montgomery County, using crashes in Fairfax County on similar roads as controls. About 7½ years after the program began, speed cameras were associated with a 10% reduction in mean speeds and a 62% reduction in the likelihood that a vehicle was traveling more than 10 mph above the speed limit at camera sites. When interviewed in Fall 2014, 95% of drivers were aware of the camera program, 62% favored it, and most had received a camera ticket or knew someone else who had. The overall effect of the camera program in its modified form, including both the law change and the corridor approach, was a 39% reduction in the likelihood that a crash resulted in an incapacitating or fatal injury. Speed cameras alone were associated with a 19% reduction in the likelihood that a crash resulted in an incapacitating or fatal injury, the law change was associated with a nonsignificant 8% increase, and the corridor approach provided an additional 30% reduction over and above the cameras. This study adds to the evidence that speed cameras can reduce speeding, which can lead to reductions in speeding-related crashes and crashes involving serious injuries or fatalities.

Fuel Consumption of Tractor-Trailer Trucks as Affected by Speed Limit and Payload Weight

DOT National Transportation Integrated Search

1975-11-01

The effect of speed limit and payload weight on fuel consumption was determined in tests of tractor-trailer rigs. Two virtually identical vehicles were used, one loaded with a 28,000 lb payload and the other carrying 42,000 lbs; each was driven over ...

Effect of Variation of Speed Limits on Intercity Bus Fuel Consumption, Coach and Driver Utilization, and Corporate Profitability

DOT National Transportation Integrated Search

1975-11-01

The effect of speed limit and passenger load on fuel consumption was determined using actual intercity buses with simulated passenger loads over different types of terrain. In addition to road tests, laboratory type measurements were made on four int...

Research on the Safety Impacts of Speed Limiter Device Installations on Commercial Motor Vehicles: Phase II

DOT National Transportation Integrated Search

2012-03-01

The purpose of this project was to identify the impacts of implementing speed limiters (SL) in commercial vehicle fleet operations. These impacts may be related to safety through a reduction in the number and/or severity of crashes, and/or address op...

75 FR 80735 - Special Conditions: Gulfstream Model GVI Airplane; High Incidence Protection

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-23

..., Aircraft Certification Service, 1601 Lind Avenue, SW., Renton, Washington, 98057-3356; telephone (425) 227... from stalling, limits the angle of attack at which the airplane can be flown during normal low speed... limit impacts the stall speed determination, the stall characteristics, the stall warning demonstration...

Appendices : evaluation of variable speed limits on I-270/I-255 in St. Louis.

DOT National Transportation Integrated Search

2010-10-01

In May of 2008, MoDOT installed a Variable Speed Limit (VSL) system along the I-270/I-255 corridor in : St. Louis. This project evaluated the VSL system and its potential impacts and benefits to the : transportation users. The technical system ...

Walking modulates speed sensitivity in Drosophila motion vision.

PubMed

Chiappe, M Eugenia; Seelig, Johannes D; Reiser, Michael B; Jayaraman, Vivek

2010-08-24

Changes in behavioral state modify neural activity in many systems. In some vertebrates such modulation has been observed and interpreted in the context of attention and sensorimotor coordinate transformations. Here we report state-dependent activity modulations during walking in a visual-motor pathway of Drosophila. We used two-photon imaging to monitor intracellular calcium activity in motion-sensitive lobula plate tangential cells (LPTCs) in head-fixed Drosophila walking on an air-supported ball. Cells of the horizontal system (HS)--a subgroup of LPTCs--showed stronger calcium transients in response to visual motion when flies were walking rather than resting. The amplified responses were also correlated with walking speed. Moreover, HS neurons showed a relatively higher gain in response strength at higher temporal frequencies, and their optimum temporal frequency was shifted toward higher motion speeds. Walking-dependent modulation of HS neurons in the Drosophila visual system may constitute a mechanism to facilitate processing of higher image speeds in behavioral contexts where these speeds of visual motion are relevant for course stabilization. Copyright 2010 Elsevier Ltd. All rights reserved.

Effect of trotting speed on kinematic variables measured by use of extremity-mounted inertial measurement units in nonlame horses performing controlled treadmill exercise.

PubMed

Cruz, Antonio M; Vidondo, Beatriz; Ramseyer, Alessandra A; Maninchedda, Ugo E

2018-02-01

OBJECTIVE To assess effects of speed on kinematic variables measured by use of extremity-mounted inertial measurement units (IMUs) in nonlame horses performing controlled exercise on a treadmill. ANIMALS 10 nonlame horses. PROCEDURES 6 IMUs were attached at predetermined locations on 10 nonlame Franches Montagnes horses. Data were collected in triplicate during trotting at 3.33 and 3.88 m/s on a high-speed treadmill. Thirty-three selected kinematic variables were analyzed. Repeated-measures ANOVA was used to assess the effect of speed. RESULTS Significant differences between the 2 speeds were detected for most temporal (11/14) and spatial (12/19) variables. The observed spatial and temporal changes would translate into a gait for the higher speed characterized by increased stride length, protraction and retraction, flexion and extension, mediolateral movement of the tibia, and symmetry, but with similar temporal variables and a reduction in stride duration. However, even though the tibia coronal range of motion was significantly different between speeds, the high degree of variability raised concerns about whether these changes were clinically relevant. For some variables, the lower trotting speed apparently was associated with more variability than was the higher trotting speed. CONCLUSIONS AND CLINICAL RELEVANCE At a higher trotting speed, horses moved in the same manner (eg, the temporal events investigated occurred at the same relative time within the stride). However, from a spatial perspective, horses moved with greater action of the segments evaluated. The detected changes in kinematic variables indicated that trotting speed should be controlled or kept constant during gait evaluation.

Pilot test of Heed the Speed, a program to reduce speeds in residential neighborhoods

DOT National Transportation Integrated Search

2006-08-01

There is abundant evidence that higher speeds are associated with more severe pedestrian injuries and increased death. Speeding is generally more dangerous for pedestrians on residential roads than on other roadways. There has been significant work o...

Development of a speeding-related crash typology

DOT National Transportation Integrated Search

2010-04-01

Speeding, the driver behavior of exceeding the posted speed limit or driving too fast for conditions, has consistently been estimated to be a contributing factor to a significant percentage of fatal and nonfatal crashes. The U.S. Department of Transp...

Experimental Evaluation of a High Speed Flywheel for an Energy Cache System

NASA Astrophysics Data System (ADS)

Haruna, J.; Murai, K.; Itoh, J.; Yamada, N.; Hirano, Y.; Fujimori, T.; Homma, T.

2011-03-01

A flywheel energy cache system (FECS) is a mechanical battery that can charge/discharge electricity by converting it into the kinetic energy of a rotating flywheel, and vice versa. Compared to a chemical battery, a FECS has great advantages in durability and lifetime, especially in hot or cold environments. Design simulations of the FECS were carried out to clarify the effects of the composition and dimensions of the flywheel rotor on the charge/discharge performance. The rotation speed of a flywheel is limited by the strength of the materials from which it is constructed. Three materials, carbon fiber-reinforced polymer (CFRP), Cr-Mo steel, and a Mg alloy were examined with respect to the required weight and rotation speed for a 3 MJ (0.8 kWh) charging/discharging energy, which is suitable for an FECS operating with a 3-5 kW photovoltaic device in an ordinary home connected to a smart grid. The results demonstrate that, for a stationary 3 MJ FECS, Cr-Mo steel was the most cost-effective, but also the heaviest, Mg-alloy had a good balance of rotation speed and weight, which should result in reduced mechanical loss and enhanced durability and lifetime of the system, and CFRP should be used for applications requiring compactness and a higher energy density. Finally, a high-speed prototype FW was analyzed to evaluate its fundamental characteristics both under acceleration and in the steady state.

High-speed and high-resolution quantitative phase imaging with digital-micromirror device-based illumination (Conference Presentation)

NASA Astrophysics Data System (ADS)

Zhou, Renjie; Jin, Di; Yaqoob, Zahid; So, Peter T. C.

2017-02-01

Due to the large number of available mirrors, the patterning speed, low-cost, and compactness, digital-micromirror devices (DMDs) have been extensively used in biomedical imaging system. Recently, DMDs have been brought to the quantitative phase microscopy (QPM) field to achieve synthetic-aperture imaging and tomographic imaging. Last year, our group demonstrated using DMD for QPM, where the phase-retrieval is based on a recently developed Fourier ptychography algorithm. In our previous system, the illumination angle was varied through coding the aperture plane of the illumination system, which has a low efficiency on utilizing the laser power. In our new DMD-based QPM system, we use the Lee-holograms, which is conjugated to the sample plane, to change the illumination angles for much higher power efficiency. Multiple-angle illumination can also be achieved with this method. With this versatile system, we can achieve FPM-based high-resolution phase imaging with 250 nm lateral resolution using the Rayleigh criteria. Due to the use of a powerful laser, the imaging speed would only be limited by the camera acquisition speed. With a fast camera, we expect to achieve close to 100 fps phase imaging speed that has not been achieved in current FPM imaging systems. By adding reference beam, we also expect to achieve synthetic-aperture imaging while directly measuring the phase of the sample fields. This would reduce the phase-retrieval processing time to allow for real-time imaging applications in the future.

Study on typhoon characteristic based on bridge health monitoring system.

PubMed

Wang, Xu; Chen, Bin; Sun, Dezhang; Wu, Yinqiang

2014-01-01

Through the wind velocity and direction monitoring system installed on Jiubao Bridge of Qiantang River, Hangzhou city, Zhejiang province, China, a full range of wind velocity and direction data was collected during typhoon HAIKUI in 2012. Based on these data, it was found that, at higher observed elevation, turbulence intensity is lower, and the variation tendency of longitudinal and lateral turbulence intensities with mean wind speeds is basically the same. Gust factor goes higher with increasing mean wind speed, and the change rate obviously decreases as wind speed goes down and an inconspicuous increase occurs when wind speed is high. The change of peak factor is inconspicuous with increasing time and mean wind speed. The probability density function (PDF) of fluctuating wind speed follows Gaussian distribution. Turbulence integral scale increases with mean wind speed, and its PDF does not follow Gaussian distribution. The power spectrum of observation fluctuating velocity is in accordance with Von Karman spectrum.

Control model design to limit DC-link voltage during grid fault in a dfig variable speed wind turbine

NASA Astrophysics Data System (ADS)

Nwosu, Cajethan M.; Ogbuka, Cosmas U.; Oti, Stephen E.

2017-08-01

This paper presents a control model design capable of inhibiting the phenomenal rise in the DC-link voltage during grid- fault condition in a variable speed wind turbine. Against the use of power circuit protection strategies with inherent limitations in fault ride-through capability, a control circuit algorithm capable of limiting the DC-link voltage rise which in turn bears dynamics that has direct influence on the characteristics of the rotor voltage especially during grid faults is here proposed. The model results so obtained compare favorably with the simulation results as obtained in a MATLAB/SIMULINK environment. The generated model may therefore be used to predict near accurately the nature of DC-link voltage variations during fault given some factors which include speed and speed mode of operation, the value of damping resistor relative to half the product of inner loop current control bandwidth and the filter inductance.

Ultrafast Imaging using Spectral Resonance Modulation

NASA Astrophysics Data System (ADS)

Huang, Eric; Ma, Qian; Liu, Zhaowei

2016-04-01

CCD cameras are ubiquitous in research labs, industry, and hospitals for a huge variety of applications, but there are many dynamic processes in nature that unfold too quickly to be captured. Although tradeoffs can be made between exposure time, sensitivity, and area of interest, ultimately the speed limit of a CCD camera is constrained by the electronic readout rate of the sensors. One potential way to improve the imaging speed is with compressive sensing (CS), a technique that allows for a reduction in the number of measurements needed to record an image. However, most CS imaging methods require spatial light modulators (SLMs), which are subject to mechanical speed limitations. Here, we demonstrate an etalon array based SLM without any moving elements that is unconstrained by either mechanical or electronic speed limitations. This novel spectral resonance modulator (SRM) shows great potential in an ultrafast compressive single pixel camera.

Operating limitations of high speed jet lubricated ball bearings

NASA Technical Reports Server (NTRS)

Zaretsky, E. V.; Signer, H.; Bamberger, E. N.

1975-01-01

A parametric study was performed with 120-mm bore angular-contact ball bearings having a nominal contact angle of 20 degrees. The bearings had either an inner- or an outer-race land riding cage, and lubrication was by recirculating oil jets which had either a single or dual orifice. Thrust load, speed, and lubricant flow rate were varied. Test results were compared with those previously reported and obtained from bearings of the same design which were under-race lubricated but run under the same conditions. Jet lubricated ball bearings were limited to speeds less than 2,500,000 DN, and bearings having inner-race land riding cages produced lower temperatures than bearings with outer-race land riding cages. For a given lubricant flow rate dual orifice jets produced lower bearing temperatures than single orifice jets, but under-race lubrication produced lower bearing temperatures under all conditions of operation with no apparent bearing speed limitation.

Recent collisional jet from a primitive asteroid

NASA Astrophysics Data System (ADS)

Novaković, Bojan; Dell'Oro, Aldo; Cellino, Alberto; Knežević, Zoran

2012-09-01

In this paper we show an example of a young asteroid cluster located in a dynamically stable region, which was produced by partial disruption of a primitive body about 30 km in size. We estimate its age to be only 1.9 ± 0.3 Myr; thus, its post-impact evolution should have been very limited. The large difference in size between the largest object and the other cluster members means that this was a cratering event. The parent body had a large orbital inclination and was subject to collisions with typical impact speeds higher by a factor of 2 than in the most common situations encountered in the main belt. For the first time, we have at our disposal the observable outcome of a very recent event to study high-speed collisions involving primitive asteroids, providing very useful constraints to numerical simulations of these events and to laboratory experiments.

A Microelectromechanical High-Density Energy Storage/Rapid Release System

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

Rodgers, M. Steven; Allen, Jim J.; Meeks, Kent D.

1999-07-21

One highly desirable characteristic of electrostatically driven microelectromechanical systems (MEMS) is that they consume very little power. The corresponding drawback is that the force they produce may be inadequate for many applications. It has previously been demonstrated that gear reduction units or microtransmissions can substantially increase the torque generated by microengines. Operating speed, however, is also reduced by the transmission gear ratio. Some applications require both high speed and high force. If this output is only required for a limited period of time, then energy could be stored in a mechanical system and rapidly released upon demand. We have designed,more » fabricated, and demonstrated a high-density energy storage/rapid release system that accomplishes this task. Built using a 5-level surface micromachining technology, the assembly closely resembles a medieval crossbow. Energy releases on the order of tens of nanojoules have already been demonstrated, and significantly higher energy systems are under development.« less

Shot-noise limited throughput of soft x-ray ptychography for nanometrology applications

NASA Astrophysics Data System (ADS)

Koek, Wouter; Florijn, Bastiaan; Bäumer, Stefan; Kruidhof, Rik; Sadeghian, Hamed

2018-03-01

Due to its potential for high resolution and three-dimensional imaging, soft x-ray ptychography has received interest for nanometrology applications. We have analyzed the measurement time per unit area when using soft x-ray ptychography for various nanometrology applications including mask inspection and wafer inspection, and are thus able to predict (order of magnitude) throughput figures. Here we show that for a typical measurement system, using a typical sampling strategy, and when aiming for 10-15 nm resolution, it is expected that a wafer-based topology (2.5D) measurement takes approximately 4 minutes per μm2 , and a full three-dimensional measurement takes roughly 6 hours per μm2 . Due to their much higher reflectivity EUV masks can be measured considerably faster; a measurement speed of 0.1 seconds per μm2 is expected. However, such speeds do not allow for full wafer or mask inspection at industrially relevant throughput.

Landing impact studies of a 0.3-scale model air cushion landing system for a Navy fighter airplane

NASA Technical Reports Server (NTRS)

Leland, T. J. W.; Thompson, W. C.

1975-01-01

An experimental study was conducted in order to determine the landing-impact behavior of a 0.3-scale, dynamically (but not physically) similar model of a high-density Navy fighter equipped with an air cushion landing system. The model was tested over a range of landing contact attitudes at high forward speeds and sink rates on a specialized test fixture at the Langley aircraft landing loads and traction facility. The investigation indicated that vertical acceleration at landing impact was highly dependent on the pitch angle at ground contact, the higher acceleration of approximately 5g occurring near zero body-pitch attitude. A limited number of low-speed taxi tests were made in order to determine model stability characteristics. The model was found to have good pitch-damping characteristics but stability in roll was marginal.

Kinetic treatment of nonlinear magnetized plasma motions - General geometry and parallel waves

NASA Technical Reports Server (NTRS)

Khabibrakhmanov, I. KH.; Galinskii, V. L.; Verheest, F.

1992-01-01

The expansion of kinetic equations in the limit of a strong magnetic field is presented. This gives a natural description of the motions of magnetized plasmas, which are slow compared to the particle gyroperiods and gyroradii. Although the approach is 3D, this very general result is used only to focus on the parallel propagation of nonlinear Alfven waves. The derivative nonlinear Schroedinger-like equation is obtained. Two new terms occur compared to earlier treatments, a nonlinear term proportional to the heat flux along the magnetic field line and a higher-order dispersive term. It is shown that kinetic description avoids the singularities occurring in magnetohydrodynamic or multifluid approaches, which correspond to the degenerate case of sound speeds equal to the Alfven speed, and that parallel heat fluxes cannot be neglected, not even in the case of low parallel plasma beta. A truly stationary soliton solution is derived.

Microelectromechanical high-density energy storage/rapid release system

NASA Astrophysics Data System (ADS)

Rodgers, M. Steven; Allen, James J.; Meeks, Kent D.; Jensen, Brian D.; Miller, Samuel L.

1999-08-01

One highly desirable characteristic of electrostatically driven microelectromechanical systems (MEMS) is that they consume very little power. The corresponding drawback is that the force they produce may be inadequate for many applications. It has previously been demonstrated that gear reduction units or microtransmissions can substantially increase the torque generated by microengines. Operating speed, however, is also reduced by the transmission gear ratio. Some applications require both high speed and high force. If this output is only required for a limited period of time, then energy could be stored in a mechanical system and rapidly released upon demand. We have designed, fabricated, and demonstrated a high-density energy storage/rapid release system that accomplishes this task. Built using a 5-level surface micromachining technology, the assembly closely resembles a medieval crossbow. Energy releases on the order of tens of nanojoules have already been demonstrated, and significantly higher energy systems are under development.

Dynamic, Hot Surface Ignition of Aircraft Fuels and Hydraulic Fluids

DTIC Science & Technology

1980-10-01

fuels on a heated stainless steel surface. Higher local surface air speeds necessitated higher surface temperatures for ignition of an applied fluid._-7...Aircraft Fuels ( stainless steel surface) 8. Air Speed and Surface Material Effects on Hot Surface 21 Ignition Temperature of Aircraft Fuels (Titanium...Material Effects on Hot Surface 26 Ignition Temperature of Aircraft Hydraulic Fluids ( Stainless steel surface) 11. Air Speed and Surface Material

Automated in-line mixing system for large scale production of chitosan-based polyplexes.

PubMed

Tavakoli Naeini, Ashkan; Soliman, Ousamah Younoss; Alameh, Mohamad Gabriel; Lavertu, Marc; Buschmann, Michael D

2017-08-15

Chitosan (CS)-based polyplexes are efficient non-viral gene delivery systems that are most commonly prepared by manual mixing. However, manual mixing is not only poorly controlled but also restricted to relatively small preparation volumes, limiting clinical applications. In order to overcome these drawbacks and to produce clinical quantities of CS-based polyplexes, a fully automated in-line mixing platform was developed for production of large batches of small-size and homogeneous CS-based polyplexes. Operational conditions to produce small-sized homogeneous polyplexes were identified. Increasing mixing concentrations of CS and nucleic acid was directly associated with an increase in size and polydispersity of both CS/pDNA and CS/siRNA polyplexes. We also found that although the speed of mixing has a negligible impact on the properties of CS/pDNA polyplexes, the size and polydispersity of CS/siRNA polyplexes are strongly influenced by the mixing speed: the higher the speed, the smaller the size and polydispersity. While in-line and manual CS/pDNA polyplexes had similar size and PDI, CS/siRNA polyplexes were smaller and more homogenous when prepared in-line in the non-laminar flow regime compared to manual method. Finally, we found that in-line mixed CS/siRNA polyplexes have equivalent or higher silencing efficiency of ApoB in HepG2 cells, compared to manually prepared polyplexes. Copyright © 2017 Elsevier Inc. All rights reserved.

Idealized modeling of convective organization with changing sea surface temperatures using multiple equilibria in weak temperature gradient simulations

NASA Astrophysics Data System (ADS)

Sentić, Stipo; Sessions, Sharon L.

2017-06-01

The weak temperature gradient (WTG) approximation is a method of parameterizing the influences of the large scale on local convection in limited domain simulations. WTG simulations exhibit multiple equilibria in precipitation; depending on the initial moisture content, simulations can precipitate or remain dry for otherwise identical boundary conditions. We use a hypothesized analogy between multiple equilibria in precipitation in WTG simulations, and dry and moist regions of organized convection to study tropical convective organization. We find that the range of wind speeds that support multiple equilibria depends on sea surface temperature (SST). Compared to the present SST, low SSTs support a narrower range of multiple equilibria at higher wind speeds. In contrast, high SSTs exhibit a narrower range of multiple equilibria at low wind speeds. This suggests that at high SSTs, organized convection might occur with lower surface forcing. To characterize convection at different SSTs, we analyze the change in relationships between precipitation rate, atmospheric stability, moisture content, and the large-scale transport of moist entropy and moisture with increasing SSTs. We find an increase in large-scale export of moisture and moist entropy from dry simulations with increasing SST, which is consistent with a strengthening of the up-gradient transport of moisture from dry regions to moist regions in organized convection. Furthermore, the changes in diagnostic relationships with SST are consistent with more intense convection in precipitating regions of organized convection for higher SSTs.

Parallel algorithms for quantum chemistry. I. Integral transformations on a hypercube multiprocessor

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

Whiteside, R.A.; Binkley, J.S.; Colvin, M.E.

1987-02-15

For many years it has been recognized that fundamental physical constraints such as the speed of light will limit the ultimate speed of single processor computers to less than about three billion floating point operations per second (3 GFLOPS). This limitation is becoming increasingly restrictive as commercially available machines are now within an order of magnitude of this asymptotic limit. A natural way to avoid this limit is to harness together many processors to work on a single computational problem. In principle, these parallel processing computers have speeds limited only by the number of processors one chooses to acquire. Themore » usefulness of potentially unlimited processing speed to a computationally intensive field such as quantum chemistry is obvious. If these methods are to be applied to significantly larger chemical systems, parallel schemes will have to be employed. For this reason we have developed distributed-memory algorithms for a number of standard quantum chemical methods. We are currently implementing these on a 32 processor Intel hypercube. In this paper we present our algorithm and benchmark results for one of the bottleneck steps in quantum chemical calculations: the four index integral transformation.« less

Effects of temperature on sustained swimming performance and swimming kinematics of the chub mackerel Scomber japonicus.

PubMed

Dickson, Kathryn A; Donley, Jeanine M; Sepulveda, Chugey; Bhoopat, Lisa

2002-04-01

The effects of a 6 degrees C difference in water temperature on maximum sustained swimming speed, swimming energetics and swimming kinematics were measured in the chub mackerel Scomber japonicus (Teleostei: Scombridae), a primarily coastal, pelagic predator that inhabits subtropical and temperate transition waters of the Atlantic, Pacific and Indian Oceans. New data for chub mackerel acclimated to 18 degrees C are compared with published data from our laboratory at 24 degrees C. Twelve individuals acclimated to each of two temperatures (15.6-26.3 cm fork length, FL, and 34-179 g at 18 degrees C; 14.0-24.7 cm FL and 26-156 g at 24 degrees C) swam at a range of speeds in a temperature-controlled Brett-type respirometer, at the respective acclimation temperature. At a given fish size, the maximum speed that S. japonicus was able to maintain for a 30-min period, while swimming steadily using slow, oxidative locomotor muscle (U(max,c)), was significantly greater at 24 than at 18 degrees C (52.5-97.5 cm s(-1) at 18 degrees C and 70-120 cm s(-1) at 24 degrees C). At a given speed and fish size, the rate of oxygen consumption (VO(2)) was significantly higher at 24 than at 18 degrees C because of a higher net cost of transport (1073-4617 J km(-1) kg(-1) at 18 degrees C and 2708-14895 J km(-1) kg(-1) at 24 degrees C). Standard metabolic rate, calculated by extrapolating the logO(2) versus swimming speed relationship to zero speed, did not vary significantly with temperature or fish mass (126.4+/-67.2 mg O(2) h(-1) kg(-1) at 18 degrees C and 143.2+/-80.3 mg O(2) h(-1) kg(-1) at 24 degrees C; means +/- S.D., N=12). Swimming kinematics was quantified from high-speed (120 Hz) video recordings analyzed with a computerized, two-dimensional motion-analysis system. At a given speed and fish size, there were no significant effects of temperature on tail-beat frequency, tail-beat amplitude or stride length, but propulsive wavelength increased significantly with temperature as a result of an increase in propulsive wave velocity. Thus, the main effects of temperature on chub mackerel swimming were increases in both U(max,c) and the net cost of swimming at 24 degrees C. Like other fishes, S. japonicus apparently must recruit more slow, oxidative muscle fibers to swim at a given sustainable speed at the lower temperature because of the reduced power output. Thus, the 24 degrees C mackerel reach a higher speed before they must recruit the fast, glycolytic fibers, thereby increasing U(max,c) at 24 degrees C. By quantifying in vivo the effects of temperature on the swimming performance of an ectothermic species that is closely related to the endothermic tunas, this study also provides evidence that maintaining the temperature of the slow, oxidative locomotor muscle at 6 degrees C or more above ambient water temperature in tunas should significantly increase sustainable swimming speeds, but also increase the energetic cost of swimming, unless cardiac output limits muscle performance.

Linear or Rotary Actuator Using Electromagnetic Driven Hammer as Prime Mover

NASA Technical Reports Server (NTRS)

McMahan, Bert K. (Inventor); Sesler, Joshua J. (Inventor); Paine, Matthew T. (Inventor); McMahan, Mark C. (Inventor); Paine, Jeffrey S. N. (Inventor); Smith, Byron F. (Inventor)

2018-01-01

We claim a hammer driven actuator that uses the fast-motion, low-force characteristics of an electro-magnetic or similar prime mover to develop kinetic energy that can be transformed via a friction interface to produce a higher-force, lower-speed linear or rotary actuator by using a hammering process to produce a series of individual steps. Such a system can be implemented using a voice-coil, electro-mechanical solenoid or similar prime mover. Where a typical actuator provides limited range of motion or low force, the range of motion of a linear or rotary impact driven motor can be configured to provide large displacements which are not limited by the characteristic dimensions of the prime mover.

Gait speed is limited but improves over the course of acute care physical therapy.

PubMed

Braden, Heather J; Hilgenberg, Sean; Bohannon, Richard W; Ko, Man-Soo; Hasson, Scott

2012-01-01

Gait is a common focus of physical therapists' management of patients in acute care settings. Walking speed, the distance a patient covers per unit time, has been advocated as a "sixth vital sign." However, the feasibility of measuring walking speed and the degree to which walking speed is limited or improves over the course of therapy in the acute care setting are unclear. The purpose of this study of patients undergoing physical therapy during acute care hospitalization, therefore, was to determine whether walking speed can be measured in acute care and whether walking speed is limited and changes over the course of therapy. This was an observational cross-sectional study. Participants were 46 hospital inpatients, mean age 75.0 years (SD = 7.8), referred to physical therapy and able to walk at least 20 ft. Information regarding diagnosis, comorbidities, physical assistance, device use, body height, and weight was obtained. Speed was determined during initial and final physical therapy visits while patients walked at their self-selected speed over a marked course in a hospital corridor. Therapists reported that walking speed was clinically feasible, requiring inexpensive, available resources, 4 minutes' additional time, and simple calculations for documentation. Initial walking speed was a mean of 0.33 m/s (SD = 0.21; 95% confidence interval [CI]: 0.27-0.39), whereas final speed was 0.37 m/s (SD = 0.20; 95% CI: 0.31-0.43). The Wilcoxon test showed the increase in walking speed (0.04 m/s) to be significant (P = .005) over a mean therapy period of 2.0 days (SD = 1.4) and total hospitalization period of 5.5 days (SD = 3.6). The effect size and standardized response mean were 0.19 and 0.36, respectively. Minimal detectable change was 0.18 m/s. Walking speed is a feasible measure for patients admitted to an acute care hospital. It shows that patients walk slowly relative to community requirements but that their speed improves even over a short course of therapy.

Comment on "Modified quantum-speed-limit bounds for open quantum dynamics in quantum channels"

NASA Astrophysics Data System (ADS)

Mirkin, Nicolás; Toscano, Fabricio; Wisniacki, Diego A.

2018-04-01

In a recent paper [Phys. Rev. A 95, 052118 (2017), 10.1103/PhysRevA.95.052118], the authors claim that our criticism, in Phys. Rev. A 94, 052125 (2016), 10.1103/PhysRevA.94.052125, to some quantum speed limit bounds for open quantum dynamics that appeared recently in literature are invalid. According to the authors, the problem with our analysis would be generated by an artifact of the finite-precision numerical calculations. We analytically show here that it is not possible to have any inconsistency associated with the numerical precision of calculations. Therefore, our criticism of the quantum speed limit bounds continues to be valid.

Evaluating safety and operations of high-speed signalized intersections.

DOT National Transportation Integrated Search

2010-03-01

This Final Report reviews a research effort to evaluate the safety and operations of high-speed intersections in the State of : Oregon. In particular, this research effort focuses on four-leg, signalized intersections with speed limits of 45 mph or :...

Evaluating safety and operation of high-speed intersections.

DOT National Transportation Integrated Search

2010-03-01

This Final Report reviews a research effort to evaluate the safety and operations of high-speed intersections in the State of : Oregon. In particular, this research effort focuses on four-leg, signalized intersections with speed limits of 45 mph or :...

Development of a speeding-related crash typology : [summary report].

DOT National Transportation Integrated Search

2010-01-01

Speeding, the driver behavior of exceeding the posted speed limit or driving too fast : for conditions, has consistently been shown to be a contributing factor to a signifcant percentage of fatal and nonfatal crashes. Between 1990 and 2006, the frequ...

Introduction of Cooperative Vehicle-to-Infrastructure Systems to Improve Speed Harmonization

DOT National Transportation Integrated Search

2016-03-01

This project executed a preliminary experiment of vehicle-to-infrastructure (V2I)-based speed harmonization in which speed guidance was communicated directly to vehicles. This experiment involved a set of micro-simulation experiments and a limited nu...

Identifying and overcoming the effect of mass transfer limitation on decreased yield in enzymatic hydrolysis of lignocellulose at high solid concentrations.

PubMed

Du, Jian; Cao, Yuan; Liu, Guodong; Zhao, Jian; Li, Xuezhi; Qu, Yinbo

2017-04-01

Cellulose conversion decreases significantly with increasing solid concentrations during enzymatic hydrolysis of insoluble lignocellulosic materials. Here, mass transfer limitation was identified as a significant determining factor of this decrease by studying the hydrolysis of delignified corncob residue in shake flask, the most used reaction vessel in bench scale. Two mass transfer efficiency-related factors, mixing speed and flask filling, were shown to correlate closely with cellulose conversion at solid loadings higher than 15% DM. The role of substrate characteristics in mass transfer performance was also significant, which was revealed by the saccharification of two corn stover substrates with different pretreatment methods at the same solid loading. Several approaches including premix, fed-batch operation, and particularly the use of horizontal rotating reactor were shown to be valid in facilitating cellulose conversion via improving mass transfer efficiency at solid concentrations higher than 15% DM. Copyright © 2017 Elsevier Ltd. All rights reserved.

14 CFR 25.1517 - Rough air speed, VRA.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Rough air speed, VRA. 25.1517 Section 25... Limitations § 25.1517 Rough air speed, VRA. A rough air speed, VRA, for use as the recommended turbulence... rough air encounters will not cause the overspeed warning to operate too frequently. In the absence of a...

Quadrupedal galloping control for a wide range of speed via vertical impulse scaling.

PubMed

Park, Hae-Won; Kim, Sangbae

2015-03-25

This paper presents a bio-inspired quadruped controller that allows variable-speed galloping. The controller design is inspired by observations from biological runners. Quadrupedal animals increase the vertical impulse that is generated by ground reaction forces at each stride as running speed increases and the duration of each stance phase reduces, whereas the swing phase stays relatively constant. Inspired by this observation, the presented controller estimates the required vertical impulse at each stride by applying the linear momentum conservation principle in the vertical direction and prescribes the ground reaction forces at each stride. The design process begins with deriving a planar model from the MIT Cheetah 2 robot. A baseline periodic limit cycle is obtained by optimizing ground reaction force profiles and the temporal gait pattern (timing and duration of gait phases). To stabilize the optimized limit cycle, the obtained limit cycle is converted to a state feedback controller by representing the obtained ground reaction force profiles as functions of the state variable, which is monotonically increasing throughout the gait, adding impedance control around the height and pitch trajectories of the obtained limit cycle and introducing a finite state machine and a pattern stabilizer to enforce the optimized gait pattern. The controller that achieves a stable 3 m s(-1) gallop successfully adapts the speed change by scaling the vertical ground reaction force to match the momentum lost by gravity and adding a simple speed controller that controls horizontal speed. Without requiring additional gait optimization processes, the controller achieves galloping at speeds ranging from 3 m s(-1) to 14.9 m s(-1) while respecting the torque limit of the motor used in the MIT Cheetah 2 robot. The robustness of the controller is verified by demonstrating stable running during various disturbances, including 1.49 m step down and 0.18 m step up, as well as random ground height and model parameter variations.

Unshrouded Centrifugal Turbopump Impeller Design Methodology

NASA Technical Reports Server (NTRS)

Prueger, George H.; Williams, Morgan; Chen, Wei-Chung; Paris, John; Williams, Robert; Stewart, Eric

2001-01-01

Turbopump weight continues to be a dominant parameter in the trade space for reduction of engine weight. Space Shuttle Main Engine weight distribution indicates that the turbomachinery make up approximately 30% of the total engine weight. Weight reduction can be achieved through the reduction of envelope of the turbopump. Reduction in envelope relates to an increase in turbopump speed and an increase in impeller head coefficient. Speed can be increased until suction performance limits are achieved on the pump or due to alternate constraints the turbine or bearings limit speed. Once the speed of the turbopump is set the impeller tip speed sets the minimum head coefficient of the machine. To reduce impeller diameter the head coefficient must be increased. A significant limitation with increasing head coefficient is that the slope of the head-flow characteristic is affected and this can limit engine throttling range. Unshrouded impellers offer a design option for increased turbopump speed without increasing the impeller head coefficient. However, there are several issues with regard to using an unshrouded impeller: there is a pump performance penalty due to the front open face recirculation flow, there is a potential pump axial thrust problem from the unbalanced front open face and the back shroud face, and since test data is very limited for this configuration, there is uncertainty in the magnitude and phase of the rotordynamic forces due to the front impeller passage. The purpose of the paper is to discuss the design of an unshrouded impeller and to examine the hydrodynamic performance, axial thrust, and rotordynamic performance. The design methodology will also be discussed. This work will help provide some guidelines for unshrouded impeller design.

High-speed wavefront modulation in complex media (Conference Presentation)

NASA Astrophysics Data System (ADS)

Turtaev, Sergey; Leite, Ivo T.; Cizmár, TomáÅ.¡

2017-02-01

Using spatial light modulators(SLM) to control light propagation through scattering media is a critical topic for various applications in biomedical imaging, optical micromanipulation, and fibre endoscopy. Having limited switching rate, typically 10-100Hz, current liquid-crystal SLM can no longer meet the growing demands of high-speed imaging. A new way based on binary-amplitude holography implemented on digital micromirror devices(DMD) has been introduced recently, allowing to reach refreshing rates of 30kHz. Here, we summarise the advantages and limitations in speed, efficiency, scattering noise, and pixel cross-talk for each device in ballistic and diffusive regimes, paving the way for high-speed imaging through multimode fibres.

Optimal speed limits for school buses on Virginia highways : a report to Virginia's Superintendent of Public Instruction.

DOT National Transportation Integrated Search

1990-01-01

On Virginia's rural interstate highways there is a three-tiered speed limit: 45 mph for school buses, 55 mph for trucks, and 65 mph for other vehicles. On the urban interstate highways, school buses are restricted to 45 mph, but other traffic has a 5...

Item-Level Time Limits Are Not a Panacea

ERIC Educational Resources Information Center

Schmitz, Florian; Wilhelm, Oliver

2015-01-01

The excellent paper by Goldhammer (this issue) deals with a most relevant and very pervasive problem of ability assessment: the evaluation of performance by considering speed and accuracy of performance. Goldhammer proposes item-level time limits as a possible remedy for individual differences in the speed-accuracy trade-off (SATO) to keep time…

Reading Faster

ERIC Educational Resources Information Center

Nation, Paul

2009-01-01

This article describes the visual nature of the reading process as it relates to reading speed. It points out that there is a physical limit on normal reading speed and beyond this limit the reading process will be different from normal reading where almost every word is attended to. The article describes a range of activities for developing…

Automation and Mankind

DTIC Science & Technology

1960-08-07

limited by the cap- abilities of the human organism in the matter of control of its processes. In our time, the speeds of technological processes are...in many cases limited by conditions of control. The speed of human reaction is limited and therefore, at pre- sent, only processes of a relatively...forwiard, It can e foreseer thast automIation will comp~letely free Mans -Pn work unler conlitions’ of high texpemratures pressures,, anid nollutA-: or

Influence of agitation speed on tannase production and morphology of Aspergillus niger FETL FT3 in submerged fermentation.

PubMed

Darah, I; Sumathi, G; Jain, K; Lim, S H

2011-12-01

Agitation speed was found to influence the tannase production and fungal growth of Aspergillus niger FETL FT3. The optimal agitation speed was at 200 rpm which produced 1.41 U/ml tannase and 3.75 g/l of fungal growth. Lower or higher agitation speeds than 200 rpm produced lower enzyme production and fungal growth. Based on the SEM and TEM micrograph observation, there was a significant correlation between agitation speed and the morphology of the fungal mycelia. The results revealed an increase of the enzyme production with the change of the fungal growth morphology from filamentous to pelleted growth forms. However, the exposure to higher shear stress with an increasing agitation speed of the shaker also resulted in lower biomass yields as well as enzyme production.

Automated speed enforcement pilot project for the Capital Beltway : feasibility of photo-radar.

DOT National Transportation Integrated Search

1992-01-01

Because of increasing difficulties in enforcing posted speed limits on the Capital Beltway around Washington, D.C., local officials proposed that experiments be conducted with photo-radar to determine if that method of automated speed enforcement (wi...

Evaluation of free flow speeds on interrupted flow facilities.

DOT National Transportation Integrated Search

2013-05-01

The efficacy of the Florida Department of Transportation (FDOT) simple model of predicting segment free flow speed by adding 5 miles per hour (mph) to the posted speed limit was compared to the performance of the new 2010 Highway Capacity Manual (HCM...

An extended heterogeneous car-following model accounting for anticipation driving behavior and mixed maximum speeds

NASA Astrophysics Data System (ADS)

Sun, Fengxin; Wang, Jufeng; Cheng, Rongjun; Ge, Hongxia

2018-02-01

The optimal driving speeds of the different vehicles may be different for the same headway. In the optimal velocity function of the optimal velocity (OV) model, the maximum speed vmax is an important parameter determining the optimal driving speed. A vehicle with higher maximum speed is more willing to drive faster than that with lower maximum speed in similar situation. By incorporating the anticipation driving behavior of relative velocity and mixed maximum speeds of different percentages into optimal velocity function, an extended heterogeneous car-following model is presented in this paper. The analytical linear stable condition for this extended heterogeneous traffic model is obtained by using linear stability theory. Numerical simulations are carried out to explore the complex phenomenon resulted from the cooperation between anticipation driving behavior and heterogeneous maximum speeds in the optimal velocity function. The analytical and numerical results all demonstrate that strengthening driver's anticipation effect can improve the stability of heterogeneous traffic flow, and increasing the lowest value in the mixed maximum speeds will result in more instability, but increasing the value or proportion of the part already having higher maximum speed will cause different stabilities at high or low traffic densities.

Mobile app reading speed test.

PubMed

Kingsnorth, Alec; Wolffsohn, James S

2015-04-01

To validate the accuracy and repeatability of a mobile app reading speed test compared with the traditional paper version. Twenty-one subjects wearing their full refractive correction glasses read 14 sentences of decreasing print size between 1.0 and -0.1 logMAR, each consisting of 14 words (Radner reading speed test) at 40 cm with a paper-based chart and twice on iPad charts. Time duration was recorded with a stop watch for the paper chart and on the App itself for the mobile chart allowing critical print size (CPS) and optimal reading speed (ORS) to be derived objectively. The ORS was higher for the mobile app charts (194±29 wpm; 195±25 wpm) compared with the paper chart (166±20 wpm; F=57.000, p<0.001). The CPS was lower for the mobile app charts (0.17±0.20 logMAR; 0.18±0.17 logMAR) compared with the paper chart (0.25±0.17 logMAR; F=5.406, p=0.009). The mobile app test had a mean difference repeatability of 0.30±22.5 wpm, r=0.917 for ORS, and a CPS of 0.0±0.2 logMAR, r=0.769. Repeatability of the app reading speed test is as good (ORS) or better (CPS) than previous studies on the paper test. While the results are not interchangeable with paper-based charts, mobile app tablet-based tests of reading speed are reliable and rapid to perform, with the potential to capture functional visual ability in research studies and clinical practice. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Evaluating safety and operation of high-speed signalized intersections : final report, March 2010.

DOT National Transportation Integrated Search

2010-03-01

This Final Report reviews a research effort to evaluate the safety and operations of high-speed intersections in the State of : Oregon. In particular, this research effort focuses on four-leg, signalized intersections with speed limits of 45 mph or :...

Summary of state speed laws, current as of January 1, 1997

DOT National Transportation Integrated Search

1997-01-01

This summary reports the status of State statutes (or regulations) that are concerned with either speed limit or speed related violations as of January 1, 1997. The summary is divided into three areas: (1) Introduction; (2) Summary Tables; and (3) a ...

A study of the feasibility of using photo-radar for traffic speed enforcement in Virginia.

DOT National Transportation Integrated Search

1993-01-01

Because of increasing difficulties in enforcing posted speed limits on the Capital Beltway around Washington, D.C., local officials proposed that experiments be conducted with photo-radar to determine if that method of automated speed enforcement (wi...

Automated feedback to foster safe driving in young drivers : Phase 2.

DOT National Transportation Integrated Search

2015-12-01

Intelligent Speed Adaptation (ISA) represents a promising approach to reduce speeding. A core principle for ISA systems is that they provide real-time feedback to drivers, prompting them to reduce speed when some threshold at or above the limit is re...

DETERMINATION OF THE SPEED OF SOUND ALONG THE HUGONIOT IN A SHOCKED MATERIAL

DTIC Science & Technology

2017-04-25

correctly predict higher speeds of sound for the higher energy shocked states. The approximations of higher shock pressures diverge progressively...List 11 FIGURES 1 Copper Hugoniot pressure-specific volume plane 4 2 Copper Hugoniot energy -specific volume plane 4 3 Comparison between rate of...volume and energy are being used. = (, ) Then by the chain rule: = | + | Dividing by dv

Effects of Stretching Speed on Mechanical Rupture of Phospholipid/Cholesterol Bilayers: Molecular Dynamics Simulation

PubMed Central

Shigematsu, Taiki; Koshiyama, Kenichiro; Wada, Shigeo

2015-01-01

Rupture of biological cell membrane under mechanical stresses is critical for cell viability. It is triggered by local rearrangements of membrane molecules. We investigated the effects of stretching speed on mechanical rupture of phospholipid/cholesterol bilayers using unsteady molecular dynamics simulations. We focused on pore formation, the trigger of rupture, in a 40 mol% cholesterol-including bilayer. The unsteady stretching was modeled by proportional and temporal scaling of atom positions at stretching speeds from 0.025 to 30 m/s. The effects of the stretching speed on the critical areal strain, where the pore forms, is composed of two regimes. At low speeds (<1.0 m/s), the critical areal strain is insensitive to speed, whereas it significantly increases at higher speeds. Also, the strain is larger than that of a pure bilayer, regardless of the stretching speeds, which qualitatively agrees with available experimental data. Transient recovery of the cholesterol and phospholipid molecular orientations was evident at lower speeds, suggesting the formation of a stretch-induced interdigitated gel-like phase. However, this recovery was not confirmed at higher speeds or for the pure bilayer. The different responses of the molecular orientations may help explain the two regimes for the effect of stretching speed on pore formation. PMID:26471872

Tail autotomy affects bipedalism but not sprint performance in a cursorial Mediterranean lizard

NASA Astrophysics Data System (ADS)

Savvides, Pantelis; Stavrou, Maria; Pafilis, Panayiotis; Sfenthourakis, Spyros

2017-02-01

Running is essential in all terrestrial animals mainly for finding food and mates and escaping from predators. Lizards employ running in all their everyday functions, among which defense stands out. Besides flight, tail autotomy is another very common antipredatory strategy within most lizard families. The impact of tail loss to sprint performance seems to be species dependent. In some lizard species, tail shedding reduces sprint speed, in other species, increases it, and, in a few species, speed is not affected at all. Here, we aimed to clarify the effect of tail autotomy on the sprint performance of a cursorial lizard with particular adaptations for running, such as bipedalism and spike-like protruding scales (fringes) on the toepads that allow high speed on sandy substrates. We hypothesized that individuals that performed bipedalism, and have more and larger fringes, would achieve higher sprint performance. We also anticipated that tail shedding would affect sprint speed (though we were not able to define in what way because of the unpredictable effects that tail loss has on different species). According to our results, individuals that ran bipedally were faster; limb length and fringe size had limited effects on sprint performance whereas tail autotomy affected quadrupedal running only in females. Nonetheless, tail loss significantly affected bipedalism: the ability for running on hindlimbs was completely lost in all adult individuals and in 72.3% of juveniles.