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1
Fitzpatrick, Kay, C. Brian Shamburger, Raymond A. Krammes, and Daniel B. Fambro. "Operating Speed on Suburban Arterial Curves." Transportation Research Record: Journal of the Transportation Research Board 1579, no. 1 (January 1997): 89–96. http://dx.doi.org/10.3141/1579-11.
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Free-flow speeds were collected at both a control section and a curve section at 14 surburban sites with horizontal curves and 10 suburban sites with vertical curves. The scatter plots of the 85th percentile speed versus approach density indicate that when the approach density is between 3 and 15 approaches per km, approach density does not influence speed. Regression analysis indicated that the curve radius for horizontal curves and the inferred design speed for vertical curves can be used to predict the 85th percentile speed on curves for vehicles on the outside lane of a four-lane divided suburban arterial. For horizontal-curve sites, a curvilinear relationship exists between curve radius and the 85th percentile speed. A linear relationship provided the best fit between the inferred design speed and the 85th percentile speed for the vertical curve sites. For the horizontal and vertical curve sites, the speed at which 85th percentile speed becomes less than the inferred design speed is lower for suburban arterials than for rural highways. Drivers on suburban horizontal curves operate at speeds greater than the inferred design speed for curves designed for speeds of 70 kph or less, whereas on rural, two-lane roadways, drivers operate at speeds greater than the inferred design speed for curves designed for speeds of 90 kph or less. For vertical curves, the speeds at which drivers operate greater than the inferred design speed are 90 kph for suburban arterials and 105 kph for rural highways. These results are within 12 kph of the observed 85th percentile speeds on nearby control sections (approximately 80 kph for suburban arterials and 100 kph on rural highways).
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Jose Andueza, Pedro. "Mathematical Models of Vehicular Speed on Mountain Roads." Transportation Research Record: Journal of the Transportation Research Board 1701, no. 1 (January 2000): 104–10. http://dx.doi.org/10.3141/1701-13.
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Mathematical models were developed to estimate vehicular speed on curves and tangents in mountain roads. The 85th percentile speed for curves was estimated by using the radius of the curve under consideration, the radius of the previous curve, sight distance in the curve, and tangent length before the curve. The average speed was calculated by using the radius of the curve under consideration, the radius of the previous curve, and sight distance. The 85th percentile and the average speed were estimated by using the radius of the previous curve and tangent length. Speeds adopted by drivers respond not to engineer’s design speed but to geometric characteristics of the road. A design procedure is proposed that takes advantage of available design speed and driver behavior on the road at the same time. On a curve, drivers consider two efficiency measures: speed and comfort. On some curves, they prefer to feel a certain degree of discomfort in exchange for obtaining greater speeds. For some geometric conditions, drivers adopt a speed that sacrifices not only comfort but also safety.
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Collins, Kent M., and Raymond A. Krammes. "Preliminary Validation of a Speed-Profile Model for Design Consistency Evaluation." Transportation Research Record: Journal of the Transportation Research Board 1523, no. 1 (January 1996): 11–21. http://dx.doi.org/10.1177/0361198196152300102.
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The validity of a speed-profile model for design consistency evaluation was tested, including (a) the speed reduction estimation ability of the model and (b) assumptions about deceleration and acceleration characteristics approaching and departing horizontal curves. Detailed speed data were collected at a sample of 10 horizontal tangent-curve sections on two-lane rural highways in Texas. The results indicate that the model provides a reasonable, albeit simplified, representation of speed profiles on horizontal alignments consisting of long tangents and isolated curves. The model provides reasonable estimates of speed reductions from long approach tangents to curves but does not account for the effect of nearby intersections on speeds. The results also indicate that the assumed 0.85 m/sec2 value is reasonable for deceleration rates approaching curves that require speed reductions but may overestimate acceleration rates departing curves. The model's assumptions that deceleration occurs entirely on the approach tangent and that speeds are constant throughout a curve were not confirmed by observed speed behavior. The observations that deceleration continues after entering a curve and that speed adjustments occur throughout a curve are indicators of the difficulty drivers experience in judging appropriate speeds through curves.
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Šeporaitis, Mindaugas, Viktoras Vorobjovas, and Audrius Vaitkus. "Evaluation of Horizontal Curve Radius Effect on Driving Speed in Two Lane Rural Road. Pilot Study." Baltic Journal of Road and Bridge Engineering 15, no. 4 (September 28, 2020): 252–70. http://dx.doi.org/10.7250/bjrbe.2020-15.503.
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This paper presents a case study of driving speed at horizontal curves in the regional road. The literature review of operating speed at horizontal curves in regional roads expresses the difference between design speed and driving speed. Driving speed was measured in ten horizontal curves on regional road No. 2610. Collected data was compared to the design speed, various design standards, and Operating Speed Prediction Models for traffic in low-volume roads. Based on result analysis, was proposed initial adjusted minimum radius of the horizontal curve based on operating speed. It is justified that proposed corrections based on operating speed ensure a credible speed limit effect on road safety. The performed experiment showed different tendencies comparing measured driving speed with permitted and design speeds. It was determined that dependent on specific curved section drivers tend to exceed posted speed limit from 17% to 98% of cases, and from 41% to 100% − the design speed in the horizontal curve. This research led to identifying the limitations of experimental research methodology. These limitations are related to experimental Site selection with different combinations of alignment elements, traffic, and accident data. A pilot study showed significant results and gave essential insights into the full-scale research plan. The results are expected to benefit both other researchers and the organisations responsible for the development and implementation of normative technical documents for road design.
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Liu, Xing Wang. "Road Curve Speed Control Engineering Study." Applied Mechanics and Materials 66-68 (July 2011): 793–97. http://dx.doi.org/10.4028/www.scientific.net/amm.66-68.793.
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Horizontal curves have been recognised as a significant safety issue for many years, a more important factor than road width, vertical clearance or sight distance. This study investigates the issue of speed selection through curves from several different perspectives. The relationship between safety and curve speed in SiChuan provinces was analysed using data from the local crash database. A sample of curves was selected and surveyed. Following this, acurve treatments for controlling Curve speed for different vehicles was developed based on many factors that has influence on safey.
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TUCKER, VANCE A. "Gliding Birds: Descending Flight of the Whitebacked Vulture, Gyps Africanus." Journal of Experimental Biology 140, no. 1 (November 1, 1988): 325–44. http://dx.doi.org/10.1242/jeb.140.1.325.
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The air speeds and sinking speeds of birds gliding at equilibrium fall in a performance area when these quantities are plotted against one another. Three curves bound the performance area: (i) a curve for minimum sinking speed at each air speed, (ii) a curve for maximum sinking speed at each air speed, and (iii) a curve dependent on the maximum lift coefficient of the wings. I have discussed curve i in a previous paper. This paper discusses the theory of curves ii and iii, which describe rapid descent in gliding birds. I used an optical tracking device (an ornithodolite) to measure air speeds and sinking speeds of 16 African white-backed vultures (Gyps africanus Salvadori) descending rapidly from altitudes 200–500 m above the ground. The ornithodolite measured the polar coordinates of a bird's position in space (relative to the ground) and recorded them on magnetic tape. The vultures had air speeds between 5.4 and 39.lms−1, and sinking speeds between 0.2 and 8.3ms−1. Most of the observations fell within the theoretical boundaries of the performance area. These data are consistent with a maximum lift coefficient of 2.2 for the wings of white-backed vultures.
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Echaveguren, Tomás, Marcelo Bustos, and Hernán de Solminihac. "Assessment of horizontal curves of an existing road using reliability concepts." Canadian Journal of Civil Engineering 32, no. 6 (December 1, 2005): 1030–38. http://dx.doi.org/10.1139/l05-056.
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Horizontal curves on road are commonly analyzed under design speed point of view, where it is assumed that the maximum speed of a vehicle in a curve is the design speed. The empirical evidence has demonstrated that when the design speed is low, the operating speed tends to be higher. This happens because of an available remaining lateral (or transverse) friction for speeds over design speed. This condition is determined by a speed limit, obtained from the demand and supply equilibrium of friction of a pavement. The difference between operating and design speeds is usually considered as the margin of safety of a horizontal curve on a road. In this study, a methodology to determine the margin of safety of an existing curve is proposed. The methodology is based on the reliability theory by which reliability of operational conditions can be analyzed by using a reliability index as a margin of safety. A case study for light vehicles is evaluated to determine high impact variables over reliability, such as, macrotexture, skid resistance, curve radius, and superelevation. The results obtained in this study demonstrated that curve radius, skid resistance, and macrotexture are variables with high impact over failure probability. In constrast, superelevation has little effect on the failure probability.Key words: reliability, horizontal curves, operating speed, skid resistance, pavement texture.
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Pratt, Michael P., Srinivas R. Geedipally, Bahar Dadashova, Lingtao Wu, and Mohammadali Shirazi. "Familiar versus Unfamiliar Drivers on Curves: Naturalistic Data Study." Transportation Research Record: Journal of the Transportation Research Board 2673, no. 6 (May 16, 2019): 225–35. http://dx.doi.org/10.1177/0361198119846481.
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Human factors studies have shown that route familiarity affects driver behavior in various ways. Specifically, when drivers become more familiar with a roadway, they pay less attention to signs, adopt higher speeds, cut curves more noticeably, and exhibit slower reaction times to stimuli in their peripheral vision. Numerous curve speed models have been developed for purposes such as predicting driver behavior, evaluating roadway design consistency, and setting curve advisory speeds. These models are typically calibrated using field data, which gives information about driver behavior in relation to speed and sometimes lane placement, but does not provide insights into the drivers themselves. The objective of this paper is to examine the differences between the speeds of familiar and unfamiliar drivers as they traverse curves. The authors identified four two-lane rural highway sections in the State of Indiana which include multiple horizontal curves, and queried the Second Strategic Highway Research Program (SHRP2) database to obtain roadway inventory and naturalistic driving data for traversals through these curves. The authors applied a curve speed prediction model from the literature to predict the speed at the curve midpoints and compared the predicted speeds with observed speeds. The results of the analysis confirm earlier findings that familiar drivers choose higher speeds through curves. The successful use of the SHRP2 database for this analysis of route familiarity shows that the database can facilitate similar efforts for a wider range of driver behavior and human factors issues.
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Pratt, Michael P., Srinivas R. Geedipally, and Minh Le. "Cross-Sectional Study of Vehicle Speeds on Rural Four-Lane Highway Curves." Transportation Research Record: Journal of the Transportation Research Board 2674, no. 10 (July 30, 2020): 15–27. http://dx.doi.org/10.1177/0361198120939096.
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Research has consistently shown that horizontal curves are often associated with increased crash rates compared with similar tangent highway sections. These crashes are often related to speed and the difficulty of judging the severity of the curve. Curve speed models are used for a variety of applications, including assessing operational characteristics, evaluating design speed, conducting spot safety analyses, and setting curve advisory speeds. However, most of the documented curve speed models apply to rural two-lane highways, while relatively few models have been developed for rural multilane highways. These types of highways may exhibit different driver behavior in curves because of their more generous geometric design and higher traffic volumes. The objective of this paper is to document models that have been developed for several types of rural four-lane highways, including undivided highways, divided highways, and freeways. The authors developed models that account for geometric characteristics like curve radius, superelevation rate, and deflection angle, as well as operational characteristics like approach tangent (TN) speed. These models were calibrated using a database of about 46,000 vehicles across 29 horizontal curve sites in central Texas.
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Anderson, Ingrid B., and Raymond A. Krammes. "Speed Reduction as a Surrogate for Accident Experience at Horizontal Curves on Rural Two-Lane Highways." Transportation Research Record: Journal of the Transportation Research Board 1701, no. 1 (January 2000): 86–94. http://dx.doi.org/10.3141/1701-11.
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A proposed speed profile model was used to estimate the reduction in 85th percentile speeds from the approach tangent to the midpoint of 1,126 horizontal curve sites on rural two-lane highways in three states. The sites were divided into eight speed-reduction intervals, the mean accident rate and mean speed reduction were computed for each category, and linear regression was performed to analyze the statistical relationship between mean accident rate and mean speed reduction. Similar analyses were performed with degree-of-curvature intervals to compare mean degree of curvature and mean speed reduction as predictors of accident experience. The results suggest that estimated speed reduction is a useful measure that helps explain how accident experience at horizontal curves on rural two-lane highways varies with degree of curvature. Horizontal curves that require speed reductions [generally, curves sharper than about 4°, a condition that corresponds with design speeds less than 100 km/h (60 mph) and estimated 85th percentile speeds less than drivers’ desired speeds on long tangents] have higher accident rates than curves that do not require speed reductions. When curve sites are grouped into speed-reduction intervals, there is a statistically significant relationship between the intervals’ mean accident rate and mean speed reduction. The mean accident rate increases approximately linearly with the mean speed reduction.
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Montella, Alfonso, Francesco Galante, Filomena Mauriello, and Massimo Aria. "Continuous Speed Profiles to Investigate Drivers' Behavior on Two-Lane Rural Highways." Transportation Research Record: Journal of the Transportation Research Board 2521, no. 1 (January 2015): 3–11. http://dx.doi.org/10.3141/2521-01.
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To improve highway design consistency, several studies developed operating speed prediction models and investigated drivers' speed behavior. Most existing models are based on spot speed data that assume constant operating speed throughout the horizontal curves and occurrence of acceleration and deceleration only on tangents. To overcome limitations associated with existing models, this study investigated continuous speed profiles with an experiment that used a high-fidelity dynamic-driving simulator on a two-lane highway. A piecewise linear regression model and locally weighted regression scatter-plot smoothing were used to remove noise in the data set while preserving underlying patterns and to identify significant changes in the speed profile. Based on the smoothed speed profiles, models to predict operating speed in curves and in tangents, deceleration and acceleration rates to be used in the operating speed profiles, and starting and ending points of constant operating speed in curve were developed. Radius of the curve notably affected not only the operating speed in the curve but also the operating speed of the tangent following the curve: the smaller the radius, the lower the operating speed of the exit tangent. Both acceleration and deceleration rates increased with curvature. This study found that operating speed was not constant along curves. On small radius curves, deceleration ended close to the center of the curve, and acceleration starts, close to the end of the curve. Increasing the curve radius, the end point of deceleration moves toward the curve's beginning, whereas the start of acceleration moves toward the center of the curve.
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Cvitanić, Dražen, and Biljana Maljković. "Determination of Applicable Adjacent Horizontal Curve Radii Using Operating Speed." PROMET - Traffic&Transportation 31, no. 4 (August 23, 2019): 443–52. http://dx.doi.org/10.7307/ptt.v31i4.3088.
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Design of curves and their adjacent elements presents the greatest safety problem on rural two-lane roads. The use of the existing alignment consistency safety criteria (design, operating speed, and driving dynamic consistency) could have some shortcomings, especially in countries where the project or design speed is in use instead of (higher) operating speed. The consequence is that the designer should use smaller cross fall on curves than needed, while the calculated side friction is lower than in reality. Further, the existing graphs of adjacent curve radii do not take into account that there is a maximum operating speed achieved for a certain radius or long tangent above which it does not increase. This paper presents a methodology for determination of adjacent horizontal curve radii, with and without tangent between, based on the operating speed models which include dependence of operating speeds on tangents and curves on speed of adjacent alignment elements as well as maximum tangent and curve speed. The developed graphs of adjacent radii at the same time include the limiting values of driving dynamic consistency criteria, so the road designer does not need to calculate permissible and demand side friction for every combination of adjacent alignment elements.
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Zhang, D., Q. Xiao, J. Wang, and K. Li. "Driver curve speed model and its application to ACC speed control in curved roads." International Journal of Automotive Technology 14, no. 2 (March 28, 2013): 241–47. http://dx.doi.org/10.1007/s12239-013-0027-x.
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Gates, Timothy J., Md Shakir Mahmud, Anthony J. Ingle, Matthew Motz, Travis Holpuch, and Peter T. Savolainen. "Evaluation of Alternative Messages and Sign Locations on Driver Response to a Dynamic Speed Feedback Sign on a Freeway Interchange Ramp." Transportation Research Record: Journal of the Transportation Research Board 2674, no. 12 (October 30, 2020): 530–41. http://dx.doi.org/10.1177/0361198120959076.
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Research was undertaken to determine effective messaging strategies and sign positions for dynamic speed feedback signs (DSFS) when used for speed management at freeway ramp curves. A field evaluation was performed in this setting to assess the impacts of a DSFS on driver speed selection and braking characteristics while approaching and entering the curve. Three feedback messaging strategies were evaluated at three sign positions in advance of the curve. Compared with the existing site (without the DSFS), the DSFS reduced curve entry speeds and improved brake response across all test conditions, particularly for heavy trucks. Overall, considering the combination of both sign position and feedback messaging strategy, the greatest benefits to driver behavior were attained when the DSFS was positioned 255 ft upstream of the curve and the feedback message included the speed number alternating with a SLOW DOWN message. The inclusion of an advisory speed panel with the DSFS did not have a substantive impact on driver behavior. Based on the findings, the continued use of DSFS as a speed reduction treatment at freeway ramp curves is recommended. Specifically, the sign should be positioned to provide adequate time for drivers to perceive and react to the message, such that comfortable braking can be accommodated while approaching the curve. However, the sign should not be placed too far in advance of the curve, as drivers may be more likely to disregard such a premature warning message. Further evaluation of DSFS under various alternative ramp configurations is recommended.
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Loktev, Alexey Alexeevich, Vadim Vadimovich Korolev, Irina Viktorovna Shishkina, and Vladislav Sergeevich Kuskov. "Selection of shape for turnout curve of high-speed switches." Transport of the Urals, no. 3 (2020): 62–67. http://dx.doi.org/10.20291/1815-9400-2020-3-62-67.
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The main factor at determination of radius of turnout curve under the conditions of comfortable driving is the limitation of centrifugal acceleration increment amount per unit time. For this reason, at designing high-speed switches it is advisable to use variable-radius curves as a turnout curve. The paper considers variable-radius curves - cubic parabola, parabola of the fourth order and sine curve. On the basis of the comparative assessment it is established that the sine curve is the most acceptable variant for using as a turnout curve in high-speed switches.
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Zeng, Xiaohui, Han Wu, Jiang Lai, and Hongzhi Sheng. "Hunting stability of high-speed railway vehicles on a curved track considering the effects of steady aerodynamic loads." Journal of Vibration and Control 22, no. 20 (August 9, 2016): 4159–75. http://dx.doi.org/10.1177/1077546315571986.
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Aerodynamic loads may have effects on the hunting stability, and the factor of curved track makes it more complicated. Therefore, considering the steady aerodynamic loads generated by crosswind and airflow in the opposite advancing direction of train, the hunting stability of high-speed railway vehicle on a curved track is studied in this paper. The changes of gravitational restoring force and creep coefficients which are caused by aerodynamic loads are considered, and the change of equilibrium position due to aerodynamic loads, centrifugal force and the factor of curved track is also in consideration. A mathematical model of a high-speed railway vehicle during curve negotiation with aerodynamic loads is set up. A program based on the model is written and verified. Using this program, the linear critical speed considering the effects of aerodynamic loads is determined by the eigenvalue analysis. This paper investigates the critical speeds in three aerodynamic conditions. Considering the aerodynamic loads, the dependence of critical speed on curve radius and super-elevation is analyzed, and the impact of aerodynamic loads on instability mode is analyzed as well. In addition, this paper obtains the dominant factors affecting critical speed and the variation tendency of critical speed with primary longitudinal stiffness by orthogonal experiments. The results show that the critical speed decreases or increases while the wind is blowing to outer rail or inner rail respectively. The aerodynamic loads produce obvious effects on the instability mode. The variation tendency of critical speed dependence on curve radius in the conditions with aerodynamic loads keeps consistent with the case without aerodynamic loads. It is seen from the orthogonal experiments that, aerodynamic loads and curve radius are the dominant factors affecting linear critical speed of vehicle on a curved track, and the linear critical speed decreases with the increasing of primary longitudinal stiffness.
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Malaghan, Vinayak, Digvijay S. Pawar, and Hussein Dia. "Modeling Acceleration and Deceleration Rates for Two-Lane Rural Highways Using Global Positioning System Data." Journal of Advanced Transportation 2021 (April 24, 2021): 1–17. http://dx.doi.org/10.1155/2021/6630876.
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Several past studies developed acceleration/deceleration rate models as a function of a single explanatory variable. Most of them were spot speed studies with speeds measured at specific locations on curves (usually midpoint of the curve) and tangents to determine acceleration and deceleration rates. Fewer studies adopted an estimated value of 0.85 m/s2 for both deceleration and acceleration rates while approaching and departing curves, respectively. In this study, instrumented vehicles with a high-end GPS (global positioning system) device were used to collect the continuous speed profile data for two-lane rural highways. The speed profiles were used to locate the speeds at the beginning and end of deceleration/acceleration on the successive road geometric elements to calculate the deceleration/acceleration rate. The influence of different geometric design variables on the acceleration/deceleration rate was analysed to develop regression models. This study also inspeced the assumption of constant operating speed on the horizontal curve. The study results indicated that mean operating speeds measured at the point of curvature (PC) or point of tangency (PT), the midpoint of curve (MC), and the end of deceleration in curve were statistically different. Acceleration/deceleration rates as a function of different geometric variables improved the accuracy of models. This was evident from model validation and comparison with existing models in the literature. The results of this study highlight the significance of using continuous speed profile data to locate the beginning and end of deceleration/acceleration and considering different geometric variables to calibrate acceleration/deceleration rate models.
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Aree, Pichai. "Analytical determination of speed-torque and speed-current curves of single-cage induction motor under supply voltage and frequency variations." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 37, no. 6 (November 5, 2018): 2279–98. http://dx.doi.org/10.1108/compel-09-2017-0404.
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Purpose An important characteristic of most induction motors is speed- or slip-torque curve. A simplified Kloss formula is widely used for describing speed-torque characteristic because it is fairly simple. Only two parameters related to break-down torque and break-down slip are regarded as input parameters. Because this simplified formula ignores an unknown parameter that is a ratio between Thevenin’s and rotor resistances, an accurate torque curve characteristic may not be fully obtained over an entire speed range. Moreover, the conventional Kloss formula does not offer a speed-torque curve calculation when motor’s supply voltages and frequencies are deviated from rated values. Hence, the purpose of this paper is to present an extension of Kloss formula, which allows a more precise estimation of speed-torque and speed-current curves of single-cage three-phase induction motors over a wide range of speeds at different motor’s operating voltages, frequencies and rotor-circuit resistances. Design/methodology/approach The analytical approach is mainly used for determining all key parameters in the Kloss formula using a known set of data such as rated torque, starting torque, break-down torque and rated speed, in which they can be obtained from motor’s manufacturer. Findings The speed-torque and speed-current curves taken from laboratory measurements are compared with those from the calculations. Good agreements between them are fully observed. Originality/value This analytical approach is useful in providing an accurate speed-torque and speed-current curves required for most steady-state analysis.
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Retting, Richard A., Hugh W. McGee, and Charles M. Farmer. "Influence of Experimental Pavement Markings on Urban Freeway Exit-Ramp Traffic Speeds." Transportation Research Record: Journal of the Transportation Research Board 1705, no. 1 (January 2000): 116–21. http://dx.doi.org/10.3141/1705-17.
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Motor vehicle crashes on curved roadway sections occur more frequently and tend to be more severe than those on straight sections. Speed is a significant factor in many crashes that occur on curves. The effects on traffic speeds of special pavement markings intended to reduce speeds on freeway exit ramps with horizontal curves were examined. An experimental pavement marking pattern was employed that narrowed the lane width of both the curve and a portion of the tangent section leading into the curve by use of a gradual inward taper of existing edgeline or exit gore pavement markings or both. Traffic speeds were analyzed before and after installation of the pavement markings at four experimental ramps in New York and Virginia. Results indicated that the markings were generally effective in reducing speeds of passenger vehicles and large trucks. The markings were associated with significant reductions in the percentages of passenger vehicles and large trucks exceeding posted exit-ramp advisory speeds.
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Purwanto, Djoko, Amelia Kusuma Indriastuti, and Kami Hari Basuki. "Hubungan antara Kecepatan dan Kondisi Geometrik Jalan yang Berpotensi Menyebabkan Kecelakaan Lalu Lintas pada Tikungan." MEDIA KOMUNIKASI TEKNIK SIPIL 21, no. 2 (June 8, 2016): 83. http://dx.doi.org/10.14710/mkts.v21i2.11234.
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To date, the traffic accident number on hairpin curve is still quite high. This is exacerbated by speeding driving behaviour of some road users.This research aims to identify the factors that cause traffic accidents and drivers’ behaviour at the curve; to review curve geometric design; and to develop a relationship among speed, curve geometric condition and the accident at the curve. This study simply reviewed three hairpin curves that were prone to be blackspots in Batang. The dominant factors that cause accidents were human error and road condition. The driver’s speeding behaviour was indicated by the speed that was lessen when entering and increase when leaving the curve. There were speed variations among vehicles in research location that could increase the number of accident. The results of the geometric review showed that the radius of all curves evaluated did not meet the standard, i.e. less than the minimum radius. Another result of this study was relationships among speed, geometric condition and accident number, as shown by the following formula: Speed = 0.095 Radius + 42.889, No. of accident = - 0.785 Radius + 0.008 Speed - 284.301, and EAN = 0.028 Speed - 1108.689.
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He, Jiao Long, Shu Guang Chen, and Xin Sheng Zhang. "Research on Technology of Highway Curve and Slope Road Segment Alignment Safety Design." Applied Mechanics and Materials 204-208 (October 2012): 1665–68. http://dx.doi.org/10.4028/www.scientific.net/amm.204-208.1665.
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In the paper, Combination curved with slope road segment on the driving experiment , The paper is analyzed the curve and slope road segment on Gradient, Horizontal Curve Radius, Speed and heart rate these variables of the inherent relation and law. The model of the relationship of the longitudinal slope and horizontal curve radius and heart rate is set up. By employing regression analysis, Conduct quantitative analysis, calculation and can be determined by the minimum horizontal curve radius value of vertical slope corresponding to at different vehicle-speeds on curved with longitudinal slope,Theoretical reference is provided for designers in the design technology research.
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Gattis, J. L., B. Finley Vinson, and Lynette K. Duncan. "Low-Speed Horizontal Curve Friction Factors." Journal of Transportation Engineering 131, no. 2 (February 2005): 112–19. http://dx.doi.org/10.1061/(asce)0733-947x(2005)131:2(112).
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Chan, Keith H. S., and Robert W. Blake. "Flight speeds of seven bird species during chick rearing." Canadian Journal of Zoology 84, no. 7 (July 1, 2006): 1047–52. http://dx.doi.org/10.1139/z06-087.
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Flight speeds of seven bird species were recorded using a hand-held Doppler radar for adult birds flying to and from foraging areas while rearing chicks. R.A. Norberg (1981. J. Anim. Ecol. 50: 473–477) predicted that birds rearing chicks should fly at speeds greater than the maximum range speed to bring the most food to their chicks as long as the associated increase in travel costs can be more than compensated for by foraging in the travel time saved. From aerodynamic and total power curves based on a range of literature values for the drag coefficient (0.05–0.4), the minimum power speed (minimum point on the U-shaped curve), and maximum range speed (a tangent to the curve from the origin at which the distance traveled per unit energy is maximized) are compared with the mean measured flight speed for each species. For all species, the mean measured flight speed was significantly less than the maximum range speed (p < 0.05), which is independent of foraging style and habitats, suggesting that flying at speeds greater than the maximum range speed may not be a practical strategy for birds rearing chicks.
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Liu, Jin Sheng. "Numerical Simulation and Optimization of Small Low-Speed Wind Tunnel Contraction Flow." Applied Mechanics and Materials 733 (February 2015): 595–98. http://dx.doi.org/10.4028/www.scientific.net/amm.733.595.
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The principle of the design of the wind-tunnel contraction is introduced; several typical contraction curves provided by former researchers are collected and compared. Using commercial Computational Fluid Dynamics (CFD) software-Fluent: Fluent. The flied quality of different contraction curves using a 3-D axial symmetric k-ε model is compared and some suggestions on the selection of the curves to different requirement are made. Witozinsky curve and Batchelor-Shaw curve prone to counter pressure at the entrance area, serious energy loss, the speed of export poor uniformity. The uniformity of the flow field is a little better of the improved 3-power curve (Xm = 0.5).5-power curve (Xm=0.5, n=7) shows low turbulence degrees, a certain advantage in energy consumption and strong stability.
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Rayner, J. M. "Estimating power curves of flying vertebrates." Journal of Experimental Biology 202, no. 23 (December 1, 1999): 3449–61. http://dx.doi.org/10.1242/jeb.202.23.3449.
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The power required for flight in any flying animal is a function of flight speed. The power curve that describes this function has become an icon of studies of flight mechanics and physiology because it encapsulates the accessible animal's flight performance. The mechanical or aerodynamic power curve, describing the increase in kinetic energy of the air due to the passage of the bird, is necessarily U-shaped, for aerodynamic reasons, and can be estimated adequately by lifting-line theory. Predictions from this and related models agree well with measured mechanical work in flight and with results from flow visualization experiments. The total or metabolic power curve also includes energy released by the animal as heat, and is more variable in shape. These curves may be J-shaped for smaller birds and bats, but are difficult to predict theoretically owing to uncertainty about internal physiological processes and the efficiency of the flight muscles. The limitations of some existing models aiming to predict metabolic power curves are considered. The metabolic power curve can be measured for birds or bats flying in wind tunnels at controlled speeds. Simultaneous determination in European starlings Sturnus vulgaris of oxygen uptake, total metabolic rate (using labelled isotopes), aerodynamic power output and heat released (using digital video thermography) enable power curves to be determined with confidence; flight muscle efficiency is surprisingly low (averaging 15–18 %) and increases moderately with flight speed, so that the metabolic power curve is shallower than predicted by models. Accurate knowledge of the power curve is essential since extensive predictions of flight behaviour have been based upon it. The hypothesis that the power curve may not in fact exist, in the sense that the cost of flight may not be perceived by a bird as a continuous smooth function of air speed, is advanced but has not yet formally been tested. This hypothesis is considered together with evidence from variation in flight behaviour, wingbeat kinematics and flight gait with speed. Possible constraints on flight behaviour can be modelled by the power curves: these include the effect of a maximum power output and a constraint on maximum speed determined by downstroke wingbeat geometry and the relationship between thrust and lift.
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Omokawa, Masahiro, Mitsuru Saito, Katsuya Tanifuji, Hitoshi Soma, and Takumi Ishii. "355820 HIGH-SPEED RUNNING OF TILTING VEHICLE USING AIR SPRINGS ON CURVED SECTION OVERLAPPED WITH VERTICAL CURVE(Bogie,Technical Session)." Proceedings of International Symposium on Seed-up and Service Technology for Railway and Maglev Systems : STECH 2009 (2009): _355820–1_—_355820–6_. http://dx.doi.org/10.1299/jsmestech.2009._355820-1_.
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Himes, Scott, Richard J. Porter, Ian Hamilton, and Eric Donnell. "Safety Evaluation of Geometric Design Criteria: Horizontal Curve Radius and Side Friction Demand on Rural, Two-Lane Highways." Transportation Research Record: Journal of the Transportation Research Board 2673, no. 3 (March 2019): 516–25. http://dx.doi.org/10.1177/0361198119835514.
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AASHTO’s A Policy on Geometric Design of Highways and Streets, 6th Edition, provides design criteria for horizontal curve elements based on the point-mass model. The model equates the centripetal force needed to navigate a horizontal curve of a specific radius traveling at the design speed to the combination of superelevation rate and side friction needed to achieve that force. Few researchers have examined the safety impacts of horizontal curve radius, superelevation rate, and design speed through crash-based research. None of the research reviewed included the effects of design speed or superelevation rate in the crash modification factors (CMFs) or functions. This research explored these factors using a negative binomial regression modeling approach based on data collected from the SHRP 2 RID 2.0 for 889 horizontal curves on rural two-lane highways in Indiana and Pennsylvania, which resulted in roadway departure crash modification functions for horizontal curve radius and side friction demand. The crash modification function for side friction demand includes an interactive component of horizontal curve radius and speed and a direct effect of superelevation rate on roadway departure crashes. The results showed that roadway departure crashes are expected to increase for decreasing curve radius, increasing posted speed limit, and decreased superelevation rate. Furthermore, curve-related CMFs were sensitive to the curve radii used in their development. CMFs developed from curves with larger radii tended to result in larger CMFs. Sample applications are provided for computing the effects of changing the horizontal curve radius, posted speed limit, or both on proposed alternatives.
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Ottesen, Jeffery L., and Raymond A. Krammes. "Speed-Profile Model for a Design-Consistency Evaluation Procedure in the United States." Transportation Research Record: Journal of the Transportation Research Board 1701, no. 1 (January 2000): 76–85. http://dx.doi.org/10.3141/1701-10.
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A speed-profile model for estimating 85th percentile speeds along horizontal alignments of rural two-lane highways in the United States is documented. The model is an evaluation tool to check for speed consistency violations on alignments with design speeds less than 100 km/h (62.1 mph). The model was calibrated by using speed and geometry data collected for 138 horizontal curves and 78 approach tangents on 29 rural highways in 5 states. A preliminary evaluation suggests that the model provides reasonable estimates of the reductions in 85th percentile speeds from an approach tangent to a horizontal curve.
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Cakir, Osman, and Suleyman Senyurt. "Harmonicity and differential equation of involute of a curve in E3." Thermal Science 23, Suppl. 6 (2019): 2119–25. http://dx.doi.org/10.2298/tsci190730401c.
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In this paper, we first give necessary conditions in which we can decide whether a given curve is biharmonic or 1-type harmonic and differential equations characterizing the regular curves. Then we research the Frenet formulas of involute of a unit speed curve by making use of the relations between the involute of a curve and the curve itself. In addition we apply these formulas to define the essential conditions by which one can determine whether the involute of a unit speed curve is biharmonic or 1-type harmonic and then we write differential equations characterizing the involute curve by means of Frenet apparatus of the unit speed curve. Finally we examined the helix as an example to illustrate how the given theorems work.
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Easa, Said M. "Improved speed-profile model for two-lane rural highways." Canadian Journal of Civil Engineering 30, no. 6 (December 1, 2003): 1055–65. http://dx.doi.org/10.1139/l03-021.
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The speed-profile model has been suggested as a valuable tool for evaluating geometric design consistency for two-lane rural highways with isolated and combined horizontal and vertical alignments. The model determines the operating speeds on the speed-change (SC) segment, which is the distance between speed-limiting curves. The speed-limiting curves are the horizontal curves and the limited sight-distance crest vertical curves on horizontal tangents, where the sight distance required by the design guides is not satisfied. The model assumes that deceleration begins where required, which implies that the next curve is visible when deceleration starts. This paper presents an extension to the speed-profile model to incorporate the effect of sight obstruction on operating speeds and deceleration rates. The SC segment may include nonlimited sight–distance crest vertical and sag vertical curves. These curves may present sight obstruction. A procedure to determine whether the sight line is obstructed is developed. If it does, simple formulas are applied for revising the operating-speed profile. The extended model is suitable for inclusion in the design consistency module of the interactive highway safety design model.Key words: speed profile, model, two-lane highways, alignments, design consistency.
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Dinh, Do Duy, and Le Tien Dung. "An application of direct method and ball-bank indicator method to determine advisory speeds for horizontal curves in Vietnam." Journal of Science and Technology in Civil Engineering (STCE) - NUCE 14, no. 1 (January 22, 2020): 136–45. http://dx.doi.org/10.31814/stce.nuce2020-14(1)-12.
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Advisory speed signs on horizontal curves have been widely used in many countries over the world to improve traffic safety; however these road signs have not been applied in Vietnam. This paper aims to use the direct method and ball-bank indicator one to determine advisory speeds for 10 horizontal curves all with speed limit of 60 km/h on National Highway No. 4A in Lang Son province. The results showed that, advisory speeds were determined by the ball-bank indicator method ranging from 40 to 45 km/h for curves with radius of 70 m or less and from 50 to 55 km/h for curves with radius varying from 75 m to 120 m. As compared to the ball bank indicator method, advisory speeds determined by the direct method were 0 – 5 km/h higher if using 85th percentile speeds of cars, but 5 – 10 km/h lower if using average speeds of trucks.
Keywords:
advisory speed limit; operating speed; horizontal curve; ball-bank indicator; traffic safety.
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Sil, Gourab, Avijit Maji, Suresh Nama, and Akhilesh Kumar Maurya. "OPERATING SPEED PREDICTION MODEL AS A TOOL FOR CONSISTENCY BASED GEOMETRIC DESIGN OF FOUR-LANE DIVIDED HIGHWAYS." Transport 34, no. 4 (July 17, 2019): 425–36. http://dx.doi.org/10.3846/transport.2019.10715.
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Researchers have studied two-lane rural highways to predict the operating speed on horizontal curves and correlated it with safety. However, the driving characteristics of four-lane-divided highways are different. Weak lane discipline is observed in these facilities, which influences vehicle speed in adjacent lane or space. So, irrespective of its lane or lateral position, vehicles in four-lane divided highways are considered free flowing only when it maintains the minimum threshold headway from any lead vehicle. Examination of two conditions is proposed to ensure the free flow. Vehicles meeting both conditions, when tracked from the preceding tangent section till the centre of the horizontal curve, are considered as free flowing. The speed data of such free flowing passenger cars at the centre of eighteen horizontal curves on four-lane divided highways is analysed to develop a linear operating speed prediction model. The developed model depends on curve radius and preceding tangent length. The operating speed of passenger car in four-lane divided highways is influenced by horizontal curve of radius 360 m or less. Further, longer tangent would yield higher operating speed at the centre of the curve. Finally, two nomograms are suggested for conventional design, consistency based design and geometric design consistency evaluation of four-lane divided horizontal curves.
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Yang, Junru, Duanfeng Chu, Rukang Wang, Meng Gao, and Chaozhong Wu. "Coupling effect modeling of driver vehicle environment factors influencing speed selections in curves." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 234, no. 7 (August 27, 2019): 2066–78. http://dx.doi.org/10.1177/0954407019870349.
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It is of significant importance to select an appropriate speed for a vehicle to drive through an upcoming curve. Previous studies have mainly taken into account the vehicle–road interaction, which lacks quantitative analysis of drivers’ driving behavior related to curve speed selections. In this study, a curve speed model derived from the vehicle–road coupling effect analysis is combined with drivers’ driving styles which are classified into aggressive and moderate styles. Moreover, a driver behavior questionnaire based analysis is carried out for quantitative identification of the above two groups of drivers, compared with the traditional vehicle-motion-indexed classification of driving styles. Unlike previous curve speed models, the proposed model not only takes the vehicle–road coupling effect into consideration, but also introduces a driving style factor which is quantified with both driver behavior questionnaire analysis and vehicle-motion-indexed classification. The proposed curve speed model was validated with the road test data. It is found that the proposed curve speed model considering both the vehicle–road interaction and drivers’ driving styles could effectively guarantee traffic safety and riding comfort in sharp curves.
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Dias, Charitha, Takashi Oguchi, and Kasun Wimalasena. "Drivers’ Speeding Behavior on Expressway Curves: Exploring the Effect of Curve Radius and Desired Speed." Transportation Research Record: Journal of the Transportation Research Board 2672, no. 17 (June 17, 2018): 48–60. http://dx.doi.org/10.1177/0361198118778931.
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Speed profiles can be considered as a key input for assessing safety, comfort and efficiency of highway or expressway segments. Therefore, understanding drivers’ speeding behavior, particularly on expressway curve sections, is important. Most previous studies have modeled the speed on highway curve sections mainly as constant or a piecewise linear profile. Such approaches may not realistically represent the properties of speed and acceleration behavior. Furthermore, mechanisms underlying the speeding behavior through curve sections have not been comprehensively studied. In this study, the minimum-jerk concept, which was originally applied in neuroscience and robotics domains, is utilized to explore drivers’ speeding behavior on expressway curve sections. GPS-based naturalistic driving data of vehicles travelling on the Tomei expressway in Japan under free-flow conditions were used to explore the applicability and validity of the proposed approach. How the proposed approach can be used to evaluate the effect of horizontal geometry and desired driving speed on drivers’ speeding and acceleration behavior on expressway curve sections is also discussed. The findings of this study could be useful in modeling speed and acceleration choice behaviors on highway curve sections which could potentially be applied in highway design consistency evaluations. Furthermore, the outputs of this study may be useful in other advanced applications, such as modeling and visualizing realistic vehicle movements in driving simulators and virtual reality applications and trajectory planning of autonomous vehicles.
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McFadden, John, and Lily Elefteriadou. "Evaluating Horizontal Alignment Design Consistency of Two-Lane Rural Highways: Development of New Procedure." Transportation Research Record: Journal of the Transportation Research Board 1737, no. 1 (January 2000): 9–17. http://dx.doi.org/10.3141/1737-02.
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Design consistency refers to the condition wherein the roadway geometry does not violate driver expectations. Operating-speed profile models are used to evaluate the consistency of a design by identifying locations with large speed variability between successive design elements. There is a direct correlation between safety and variability in speeds. Recent operating-speed models predict the 85th percentile speeds on horizontal curves and compare this value with the expected 85th percentile speed on the approach tangent. There is a direct correlation between speed variability between successive design elements and crash rates. Eighty-fifth percentile speeds, however, do not necessarily represent the speed reductions experienced by drivers. The primary objective of the research was to assess the efficacy of the use of 85th percentile speed by operating-speed profile models to evaluate the consistency of a design. Speed data were collected at 21 horizontal curve sites. These data were used to evaluate the implication of using 85th percentile speed for evaluating design consistency. A new parameter was investigated for analyzing design consistency: the 85th percentile maximum reduction in speed (85MSR). This parameter is calculated by using each driver’s speed profile from an approach tangent through a horizontal curve and determining the maximum speed reduction each driver experiences. These maximum speed reductions are sorted, and the 85th percentile value becomes the statistic of interest, or 85MSR. 85MSR was compared with the difference in 85th percentile speeds (85S), and it was found that 85MSR is significantly larger than 85S. The data showed that, on average, 85MSR is approximately two times larger than 85S. Models were developed that predict 85MSR as a function of geometric design elements, and these models could be used to complement existing operating-speed models.
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Loktev, Alexey Alexeevich, Vadim Vadimovich Korolev, Irina Viktorovna Shishkina, and Mikhail Evgenyevich Berezovskiy. "Calculation of the speed of movement on the side track for flat grades of switches." Transport of the Urals, no. 2 (2020): 52–56. http://dx.doi.org/10.20291/1815-9400-2020-2-52-56.
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There is a need to speed up the design and implementation of switches on the operated railway network, which can significantly increase the allowed speed of trains, especially on the side track. One of the starting points in the design of switches for high speeds is to provide passengers with a comfortable ride when the train is moving on a side track by limiting the values of the so-called centrifugal acceleration and the increment (change) of the centrifugal acceleration per unit of time (second). If it is necessary to implement the speed of movement on the switch to the side track over 50 km/h, the main factor in determining the radius of the transfer curve under the conditions of driving comfort is to limit the amount of increment (change) of the centrifugal acceleration per unit of time (second). Based on this, when designing switches for high speeds, it is advisable to use curves of variable radius as a translation curve.
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Wang, Hongwei, Cheong-fat Chan, and Chiu-sing Choy. "High Speed Curve Interpolating D/A Converter." Journal of VLSI Signal Processing-Systems for Signal, Image, and Video Technology 38, no. 1 (August 2004): 5–11. http://dx.doi.org/10.1023/b:vlsi.0000028529.51311.5a.
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Di Santo, Valentina, Christopher P. Kenaley, and George V. Lauder. "High postural costs and anaerobic metabolism during swimming support the hypothesis of a U-shaped metabolism–speed curve in fishes." Proceedings of the National Academy of Sciences 114, no. 49 (November 20, 2017): 13048–53. http://dx.doi.org/10.1073/pnas.1715141114.
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Swimming performance is considered a key trait determining the ability of fish to survive. Hydrodynamic theory predicts that the energetic costs required for fishes to swim should vary with speed according to a U-shaped curve, with an expected energetic minimum at intermediate cruising speeds and increasing expenditure at low and high speeds. However, to date no complete datasets have shown an energetic minimum for swimming fish at intermediate speeds rather than low speeds. To address this knowledge gap, we used a negatively buoyant fish, the clearnose skate Raja eglanteria, and took two approaches: a classic critical swimming speed protocol and a single-speed exercise and recovery procedure. We found an anaerobic component at each velocity tested. The two approaches showed U-shaped, though significantly different, speed–metabolic relationships. These results suggest that (i) postural costs, especially at low speeds, may result in J- or U-shaped metabolism–speed curves; (ii) anaerobic metabolism is involved at all swimming speeds in the clearnose skate; and (iii) critical swimming protocols might misrepresent the true costs of locomotion across speeds, at least in negatively buoyant fish.
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Su, Xing Ye, Qin Li, and Fu Bao Li. "Speed-up and Speed-down Controller of Step Motor Based on SCM." Applied Mechanics and Materials 121-126 (October 2011): 1712–16. http://dx.doi.org/10.4028/www.scientific.net/amm.121-126.1712.
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In order to prevent the locked rotor, step-out and super ledge speed control of step motor, speed-up and speed-down control to the step motor should be carried out. Based on the speed -up curve analysis, using of symmetrical design, this paper has simplified the speed-up and speed-down curve. In order to achieve real-time computing exponential curve in SCM, using the method of constant duration and control pulses, speed-up and speed-down control, exponentially, are achieved, and, the connections between step motor and drive and circuit have been designed.
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Said, Dalia, Yasser Hassan, and A. O. Abd El Halim. "Comfort thresholds for horizontal curve design." Canadian Journal of Civil Engineering 36, no. 9 (September 2009): 1391–402. http://dx.doi.org/10.1139/l09-075.
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A key to better geometric design of highways is designing horizontal curves conforming to driver behaviour. The values of side friction factors in the point mass formula, used for the design of the minimum radius of a horizontal curve, are based on the upper threshold of driver comfort. In the current guidelines, these driver comfort levels were established in research work carried out back in the 1930s. Recently, it was found that faster drivers tend to accept higher comfort thresholds to maintain their speed and minimize speed reduction between curve and tangent. An experiment was designed at Carleton University to collect newer data on driver behaviour including speed and lateral acceleration. The results confirmed the need to revise the values of side friction demand especially for sharp curves. In addition, a model was developed to determine the side friction factor to be used in design or in consistency evaluation of horizontal curves on rural roads and ramps.
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Red, Edward. "A dynamic optimal trajectory generator for Cartesian Path following." Robotica 18, no. 5 (September 2000): 451–58. http://dx.doi.org/10.1017/s0263574700002629.
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This paper considers a dynamic and adaptive trajectory generator for negotiating paths using S-curves. Applying constant jerk transitions between the constant acceleration and deceleration periods of the trajectory, the trajectory will optimally transition to the desired speed setting. Optimal is defined to be the minimum time to transition from the current speed to the set speed for the move segment when jerk and acceleration are limited. The S-curve equations will adapt to instantaneous changes in speed setting and path length. An integrated motion planner will determine allowable speeds and transitional profiles based on the remaining move distance.
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Nezafat, Reza Vatani, Ehsan Beheshtitabar, Mecit Cetin, Elizabeth Williams, and George F. List. "Modeling and Evaluating Traffic Flow at Sag Curves When Imposing Variable Speed Limits on Connected Vehicles." Transportation Research Record: Journal of the Transportation Research Board 2672, no. 20 (July 11, 2018): 193–202. http://dx.doi.org/10.1177/0361198118784169.
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Sag curves, road segments where the gradient changes from downwards to upwards, generally reduce the roadway capacity and cause congestion. This results from a change in longitudinal driving behavior when entering a sag curve as drivers tend to reduce speeds or increase headways as vehicles reach the uphill section. In this research, a control strategy is investigated through manipulating the speed of connected vehicles (CVs) in the upstream of the sag curve to avoid the formation of bottlenecks caused by the change in driver behavior. Traffic flow along a sag curve is simulated using the intelligent driver model (IDM), a time-continuous car-following model. A feedback control algorithm is developed for adjusting the approach speeds of CVs so that the throughput of the sag curve is maximized. Depending on the traffic density at the sag curve, adjustments are made for the speeds of the CVs. A simulation-based optimization method using a meta-heuristic algorithm is employed to determine the critical control parameters. Various market penetration rates for CVs are also considered in the simulations. Even at relatively low market penetration rates (e.g., 5–10%), significant improvements in travel times and throughput are observed.
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Medina, Alberto M. Figueroa, and Andrew P. Tarko. "Speed Factors on Two-Lane Rural Highways in Free-Flow Conditions." Transportation Research Record: Journal of the Transportation Research Board 1912, no. 1 (January 2005): 39–46. http://dx.doi.org/10.1177/0361198105191200105.
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The mean free-flow speed and its variability across drivers are considered important safety factors. Despite a large body of research on operating speeds, there is still much to learn about the factors of free-flow speeds, especially on tangent segments of two-lane rural highways. The roadway factors of speed dispersion across drivers are largely unknown. Also, the use of the entire free-flow speed distribution suggested by other authors has not yet been addressed. Consequently, the existing models are not aimed to evaluate the speed variability at a site. This paper presents free-flow speed models that identify factors of mean speed and speed dispersion on tangent segments and horizontal curves of two-lane rural highways. Ten highway variables, six of them functioning as both mean speed and speed dispersion factors, were identified as speed factors on tangent segments. Four highway and curve variables, two of them functioning as both mean speed and speed dispersion factors, were identified as speed factors on horizontal curves. The developed free-flow speed models have the same prediction capabilities as traditional ordinary-least-squares models developed for specific percentile speeds. The advantages of the developed models include predicting any user-specified percentile, involving more highway characteristics as speed factors than traditional regression models, and separating the impacts on mean speed from the impacts on speed dispersion.
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Ohnuma, Hayato, Masanobu Tachi, Akihito Kumano, and Yuichi Hirano. "How To Maintain Maximal Straight Path Running Speed on a Curved Path in Sprint Events." Journal of Human Kinetics 62, no. 1 (June 13, 2018): 23–31. http://dx.doi.org/10.1515/hukin-2017-0175.
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Abstract This study aims to clarify the ideal technique for running on a curved path during sprinting events. Participants were twelve male track and field athletes including long jumpers and sprinters. The participants performed a 60-m sprint with maximal effort on straight and curved paths. Participants were divided into “good curve runners” and “poor curve runners” according to the curved path running speed relative to that of the straight path. Kinematic variables and ground reaction forces (GRFs) were registered and compared between the groups and paths. The running speed, step length, and flight distance of the outside leg on the curved path were lower than on the straight path only in poor curve runners. The medial-lateral GRF and impulse showed an increase during curved path running for both groups. However, the maximum posterior GRF and impulse decreased only in poor curve runners. The ideal technique for running on a curved path is to maintain the same kinematics and kinetics in the sagittal plane as on a straight path.
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Q, Li Jun, and Bin Liang. "Research on S-Curve Speed Control for Step Motor Based on the MCU." Applied Mechanics and Materials 273 (January 2013): 709–13. http://dx.doi.org/10.4028/www.scientific.net/amm.273.709.
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This paper researches the algorithm and equation of S curve, and realizes the process of discretization which converts curves to pulses. Finally, the experiment proved that the algorithm of S-curve of acceleration and deceleration control methods can improve the efficiency and stability of step motor.
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Martinez-Roman, J., and L. Serrano-Iribarnegaray. "Determining torque–speed curve of two-speed deep cage lift asynchronous machines." IEE Proceedings - Electric Power Applications 152, no. 3 (2005): 455. http://dx.doi.org/10.1049/ip-epa:20040988.
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Lian, Guofu, Yang Zhang, Hao Zhang, Xu Huang, Changrong Chen, and Jibin Jiang. "Investigation of Geometric Characteristics in Curved Surface Laser Cladding with Curve Path." Metals 9, no. 9 (August 29, 2019): 947. http://dx.doi.org/10.3390/met9090947.
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Laser cladding on curved surfaces is essential in industrial applications for restoration and remanufacturing of high-value parts. This study investigated the influence of different factors on clad width, clad height, and dilution rate in curved surface laser cladding with curved path. Mathematical models were developed using central composite designs to predict these geometric characteristics by controlling laser power, scanning speed, gas flow, and altering the outside radius of the cylindrical substrate. Analysis of variance and response surface methodology indicated that clad width increased with increasing laser power and reducing scanning speed. Clad height positively correlated to laser power and negatively correlated to the outside radius of the cylindrical substrate. Increasing the laser power while decreasing the scanning speed led to an increase in dilution rate. Afterwards, the geometric characteristics of the clad were improved by optimizing these factors with the target to maximize clad width and height as well as to minimize dilution rate. The difference between model predictions and experimental validations for clad width, clad height, and dilution rate were 3.485%, 3.863%, and 6.566%, respectively. The predicted accuracy was verified with these models, and they were able to provide theoretical guidance to predict and control the geometric characteristics of curved surface laser cladding with a curved path.
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Felipe, Emmanuel, and Francis Navin. "Automobiles on Horizontal Curves: Experiments and Observations." Transportation Research Record: Journal of the Transportation Research Board 1628, no. 1 (January 1998): 50–56. http://dx.doi.org/10.3141/1628-07.
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Statistical information on the basic variables involved in driving through a horizontal curve was obtained using a 4×4 Latin square design experiment to measure the action of automobile drivers in test track horizontal curves. The independent variables used in the test curves were speed (comfortable, fast); pavement surface (dry, wet); driver (male, female); and curve radius (16 m, 26 m, 60 m, 100 m). The measured output was the driver’s selected speed and corresponding lateral acceleration. In addition, the passengers indicated their comfort level on a four-point semantic scale. Expert drivers also drove the test curves to establish the upper limits of the driver-vehicle-tire system. Field observations of four curves along a two-lane rural mountain highway measured driver vehicle speed, lateral acceleration, and lateral position. The results indicate that, for a comfortable ride, drivers are limited by their comfortable lateral acceleration on small radius curves and seek the “environmental speed” on large radius curves.
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Han, Katherine. "Can Physics Help Athletes Run Faster on a Curve Track." International Journal of Physical Education, Fitness and Sports 7, no. 3 (September 26, 2018): 24–31. http://dx.doi.org/10.26524/ijpefs1833.
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Sprinting on a curve is slower than sprinting on a straight lane. To explain this phenomenon, various models based on a combination of biological and physical assumptions have been developed. These models depend on detailed parameters that significantly differ for each individual athlete. Here, we propose a general model solely based on kinetic theory of physics that can be universally applied to all athletes. By solving the force and torque equations for the running speed of the athletes on a curved track, we analyzed sprinting speeds between the inner and outer curves. Applying the data from the classic works into our models, we find that our results and conclusions are mostly aligned with the previous works while our approach is built on the accurate physics principles and contains no uncontrollable parameters. Further we show how runners can alleviate the centrifugal effect of curved track by tilting their bodies and we quantitatively determine the optimal tilting angle for a given curvature.
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Maljković, Biljana, and Dražen Cvitanić. "Evaluation of design consistency on horizontal curves for two-lane state roads in terms of vehicle path radius and speed." Baltic Journal of Road and Bridge Engineering 11, no. 2 (June 27, 2016): 127–35. http://dx.doi.org/10.3846/bjrbe.2016.15.
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Experimental investigation was conducted on a 24 km long segment of the two-lane state road to collect the driver behavior data. The research involved 20 drivers driving their own cars equipped with the GPS device. Considering the impact of path radius and speed on the side friction demand, the design consistency on horizontal curves was evaluated by determining the margins of safety. The analysis showed that the vehicle path radii were mainly smaller than curve radius, on average for 12%. Regression analysis indicated that the percentage difference between the curve radius and vehicle path radius is not affected by the speed, speed differential and geometric characteristics of the curve and surrounding elements. Two different margins of safety were analyzed. One is the difference between maximum permissible side friction (based on design speed) and side friction demand, while another is the difference between side friction supply (based on operating speed) and side friction demand. Generally, demands exceeded supply side friction factors on curves with radii smaller than 150 m, whereas “poor” conditions (in terms of Lamm’s consistency levels) were noted for curves under approximately 220 m. Both values are very close to the critical radius below which higher accident rates were observed according to several accident studies. Based on the results of the research, it is proposed to use a 12% smaller curve radius for the evaluation of margin of safety and that curves with radii smaller than 200 m should be avoided on two-lane state roads outside the built-up area.