931 research outputs found
Robustness of roundabout metering systems (RMS)
No full textA simple explorative study shows that roundabouts are too small to be equipped with permanently operating traffic lights. The conclusion of a recent, more detailed study was not fundamentally different to this: at a small two-lane roundabout with four legs and with leg-by-leg control the shortest green time is 11 to 13 seconds, irrespective of the volume of traffic on the least busy leg. This results in a great deal of unnecessary waiting time. Leg-by-leg control at a four-lane roundabout is therefore not regarded as a robust solution. In view of this, at small roundabouts incidental metering signals are used. At single lane roundabouts, metering signals provide a more balanced distribution of the waiting time, whereas at two-lane roundabouts, the metering signals also have the potential to improve traffic flow. This was shown as early as 2003, in research conducted in collaboration with the author. This article explains the theoretical background to the research. In addition, general design principles for roundabout metering signals (RMS) are deduced. In 2011, research carried out as part of a Master's thesis supervised by the author studied the robustness of RMS for various traffic loads and roundabout types. Two types of roundabout were studied: \u95 a standard turbo roundabout and \u95 a spiral roundabout. A simulation model was used that underestimated rather than overestimated the effect of an RMS. The results show that, even under less than optimum conditions, traffic performance of the whole roundabout was improved by approximately 10 %. Traffic performance in the relevant (saturated) leg improved by more than this, namely by 15-45 %. The reduction of time loss at all legs taken together is even greater: -20 % to -50 % in total, and as much as -70 % for the saturated leg. Notably, altering a dominant load pattern can even reduce waiting time in the leg with the metering light.Transport and PlanningCivil Engineering and Geoscience
Quality certi"cation and performance of Brazilian "rms: An empirical study
No full textAbstract The paper studies the relationship between quality certi"cation, as indicated by the ISO 9001 and 9002 certi"cates, and the performance of Brazilian "rms since 1992. The comparison between the group of certi"ed "rms and an especially constructed control group indicated that, as a rule, one cannot discern di!erential levels of performance across the two groups for di!erent indicators
A 23.8–30.4-GHz Vector-Modulated Phase Shifter With Two-Stage Current-Reused Variable-Gain Amplifiers Achieving 0.23° Minimum RMS Phase Error
No full textThis letter presents a millimeter-wave (mm-wave) vector-modulated phase shifter (VMPS) for phased-array applications. To improve the phase-shift accuracy without drastically increasing design complexity, the proposed VMPS structure employs variable-gain amplifiers (VGAs) that offer 2× better resolution at their low-gain states compared to their high-gain states. A two-stage current-reused structure is also proposed to implement the desired VGAs with minimal layout complexity, negligible gain penalty, and no extra power. Moreover, the proposed VMPS can maintain its phase-shift accuracy even at lower voltage gains. Fabricated in 40-nm CMOS, the prototype core consumes 11 mW from a 1.1-V supply and occupies a core area of 0.19 mm2. At 28 GHz, with a phase resolution of 0.61°, the measured RMS phase error is 0.23° at the maximum gain and remains <0.5∘ at 9-dB gain back-off. With a fixed set of VGA’s codewords, the RMS phase error and gain variation error are, respectively, lower than 1° and 0.24-dB over a bandwidth of 23.8–30.4 GHz.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic
An Algorithm for Calculating the RMS Value of the Non-Sinusoidal Current Used in AC Resistance Spot Welding
No full text
In this paper, an algorithm based on a model analysis of the online calculation of the root-mean-square (RMS) value of welding current for single-phase AC resistance spot welding (RSW) was developed. The current is highly nonlinear and typically non-sinusoidal, which makes the measuring and controlling actions difficult. Though some previous methods focused on this issue, they were so complex that they could not be effectively used in general cases. The electrical model of a single-phase AC RSW was analyzed, and then an algorithm for online calculation of the RMS value of the welding current was presented. The description includes two parts, a model-dependent part and a model-independent part. Using a previous work about online measurement of the power factor angle, the first part can be solved. For the second part, although the solution of the governing equation can be directly obtained, a lot of CPU time must be consumed due to the fact that it involves a lot of complex calculations. Therefore, a neural network was employed to simplify the calculations. Finally, experimental results and a corresponding analysis showed that the proposed algorithm can obtain the RMS values with a high precision while consuming less time when compared to directly solving the equations.</p
Uncertainty of a RMS Power Detector
No full textThe accuracy of a true-RMS detector board based on the Analog Devices LTC5596 is determined by measuring the input power and the output voltage. A number of samples of the output voltage is taken and the mean and standard deviation is shown. These measurements are done for single-tone excitation with a direct connection and over-the-air setup, and for multi-tone excitation with a direct connection. It has been demonstrated that the detector response worsens with over-the-air excitation, resulting in a doubling of the standard deviation in the output voltage compared to a direct connection. With multi-tone excitation, the standard deviation is fifteen times higher than with a direct connection. Additionally, with multi-tone excitation the mean output voltage is lower than with the same input power as single-tone. This discrepancy increases with the amount of tones.A Keysight Advanced Design System simulation is also presented for the three different measurement setups. With the use of a Monte Carlo simulation uncertainty bounds between the function generator and the power detector are made. Furthermore the noise of the power detector is simulated and sources of noise analyzed
Static and dynamic aspects of the rms local slope of growing random surfaces
No full textIn this work, we investigated static and dynamic aspects of the rms local surface slope ‘‘ρ’’ for self-affine random surfaces. The rms local slope is expressed as a function of the rms roughness amplitude σ, the in-plane correlation length ξ, and the roughness exponent H (0<H<1), as well as is shown to scale as ρ~σξ^-H. Application to room temperature heteroepitaxial silver films shows the rms local slope to be closely time invariant in the thickness range 10<h<1000 nm with an asymptotic value ρ≈0.7. However, discrepancies in deposition details could alter the mode of film growth leading to a power law growth of the local slope as a function of the film thickness h; ρ∝h^c (c>0).
Skin-Friction Measurements on Mathematically Generated Roughness in a Turbulent Channel Flow
No full textEngineering systems are affected by surface roughness, however, predicting frictional drag has proven to be challenging. The present work takes a systematic approach by generating and manufacturing surfaces roughness where surface statistics, such as rms, skewness and power-spectral density can be controlled. The frictional drag on these surfaces is measured in a turbulent channel flow facility
Control of the RMS Output Current in Series Resonant Converters
No full textYoung Author AwardsInternational audienceIn this work the problem of regulation of the Root Mean Square (RMS) value of the current for Series Resonant Converter (SRC) is addressed. The self-oscillating behavior is ensured by an amplitude-modulation like control law and the RMS value is estimated with a proposed hybrid system. The closed-loop regulation is done with a Proportional-Integral (PI) controller with anti-windup scheme, and a set of Linear Matrix Inequalities (LMIs) is introduced to tune the gains. The knowledge of a reference trajectory is not needed to implement the controller, and it is shown to be effective in simulation considering uncertain parameters
Reynolds numbers near the ultimate state of turbulent Rayleigh-Bénard convection
No full textWe report on measurements of the mean-flow Reynolds number ReU and the rms fluctuation Reynolds number ReV in turbulent Rayleigh-Bénard convection as a function of the Rayleigh number Ra for 4 x 1011 < Ra < 2 1014 and Pr ' 0:8. Both can be described by the same power law with an effective exponent = 0:44, in agreement with predictions for ReU but in disagreement with predictions for ReV
Combining Performance and Flexibility for RMS with a Hybrid Architecture
No full textAuthor supplied
Combining Performance and Flexibility for RMS
with a Hybrid Architecture
Dani¨el Telgen
12?
, Leo van Moergestel
1
, Erik Puik
1
, Pascal Muller
1
,
Arjan Groenewegen
1
, Dick van der Steen
1
, Dennis Koole
1
,
Patrick de Wit
1
, Arjen van Zanten
1
, and John-Jules Meyer
2
1
Department of Micro Systems Technology and Embedded Systems
HU University of Applied Sciences Utrecht
Nijenoord 1, 3552AS Utrecht, The Netherlands
Reconfigurable Manufacturing Systems (RMS) provide a new
step for Agile Manufacturing. RMS consist of modular manufacturing
systems that can be customized for the latest product demand. There
are many research projects concerning RMS. However, not many imple-
mentations have made it into industry. The requirements of the control
software is an important aspect, which has unique aspects to create max-
imum flexibility that becomes very complex for the software to control.
To deal with this challenge, the software needs to have high performance
and show intelligent properties to create more flexibility. This paper dis-
cusses these properties, the basic performance, and it shows how a hy-
brid system, using Robot Operating System (ROS), MongoDB, and Java
Agent Development Framework (JADE) could be the basis for further
development and be made feasible for industrial us
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