4,290 research outputs found
An experimental laboratory bench setup to study electric vehicle antilock braking / traction systems and their control
This paper describes the preliminary research and implementation of an experimental test bench set up for an electric vehicle antilock braking system (ABS)/traction control system (TCS) representing the dry, wet and icy road surfaces. A fuzzy logic based controller to control the wheel slip for electric vehicle antilock braking system is presented. The test facility comprised of an induction machine load operating in the generating region. The test facility was used to simulate a variety of tire/road μ-σ driving conditions, eliminating the initial requirement for skid-pan trials when developing algorithms. Simulation studies and results are provided
Production-decay interferences at NLO in QCD for t-channel single-top production
We present a calculation of O(\alpha_s) contributions to the process of
t-channel single-top production and decay, which include virtual and real
corrections arising from interference of the production and decay subprocesses.
The calculation is organized as a simultaneous expansion of the matrix elements
in the couplings \alpha_{ew},\alpha_s and the virtuality of the intermediate
top quark, (p_t^2-m_t^2)/m_t^2 ~ \Gamma_t/m_t, and extends earlier results
beyond the narrow-width approximation.Comment: 33 pages, 6 Figure
Application of Fuzzy control algorithms for electric vehicle antilock braking/traction control systems
Abstract—The application of fuzzy-based control strategies has recently gained enormous recognition as an approach for the rapid development of effective controllers for nonlinear time-variant systems. This paper describes the preliminary research and implementation of a fuzzy logic based controller to control the wheel slip for electric vehicle antilock braking systems (ABSs).
As the dynamics of the braking systems are highly nonlinear and time variant, fuzzy control offers potential as an important tool for development of robust traction control. Simulation studies are employed to derive an initial rule base that is then tested on an experimental test facility representing the dynamics of a braking system. The test facility is composed of an induction machine load operating in the generating region. It is shown that the
torque-slip characteristics of an induction motor provides a convenient platform for simulating a variety of tire/road - driving conditions, negating the initial requirement for skid-pan trials when developing algorithms. The fuzzy membership functions were subsequently refined by analysis of the data acquired from the test facility while simulating operation at a high coefficient of friction. The robustness of the fuzzy-logic slip regulator is further
tested by applying the resulting controller over a wide range of operating conditions. The results indicate that ABS/traction control may substantially improve longitudinal performance and offer significant potential for optimal control of driven wheels, especially under icy conditions where classical ABS/traction control schemes are constrained to operate very conservatively
High-resolution 3D weld toe stress analysis and ACPD method for weld toe fatigue crack initiation
Weld toe fatigue crack initiation is highly dependent on the local weld toe stress-concentrating geometry including any inherent flaws. These flaws are responsible for premature fatigue crack initiation (FCI) and must be minimised to maximise the fatigue life of a welded joint. In this work, a data-rich methodology has been developed to capture the true weld toe geometry and resulting local weld toe stress-field and relate this to the FCI life of a steel arc-welded joint. To obtain FCI lives, interrupted fatigue test was performed on the welded joint monitored by a novel multi-probe array of alternating current potential drop (ACPD) probes across the weld toe. This setup enabled the FCI sites to be located and the FCI life to be determined and gave an indication of early fatigue crack propagation rates. To understand fully the local weld toe stress-field, high-resolution (5 mu m) 3D linear-elastic finite element (FE) models were generated from X-ray micro-computed tomography (mu-CT) of each weld toe after fatigue testing. From these models, approximately 202 stress concentration factors (SCFs) were computed for every 1 mm of weld toe. These two novel methodologies successfully link to provide an assessment of the weld quality and this is correlated with the fatigue performance
Nuclear liquid-gas phase transition and supernovae evolution
It is shown that the large density fluctuations appearing at the onset of the
first order nuclear liquid-gas phase transition can play an important role in
the supernovae evolution. Due to these fluctuations, the neutrino gas may be
trapped inside a thin layer of matter near the proto-neutron star surface. The
resulting increase of pressure may induce strong particle ejection a few
hundred milliseconds after the bounce of the collapse, contributing to the
revival of the shock wave. The Hartree-Fock+RPA scheme, with a finite-range
nucleon-nucleon effective interaction, is employed to estimate the effects of
the neutrino trapping due to the strong density fluctuations, and to discuss
qualitatively the consequences of the suggested new scenario.Comment: version2 - precise that nuclear liquid-gas phase transition is 1st
order and the unique instable mode is isoscala
A second-order class-D audio amplifier
Class-D audio amplifiers are particularly efficient, and this efficiency has led to their ubiquity in a wide range of modern electronic appliances. Their output takes the form of a high-frequency square wave whose duty cycle (ratio of on-time to off-time) is modulated at low frequency according to the audio signal. A mathematical model is developed here for a second-order class-D amplifier design (i.e., containing one second-order integrator) with negative feedback. We derive exact expressions for the dominant distortion terms, corresponding to a general audio input signal, and confirm these predictions with simulations. We also show how the observed phenomenon of “pulse skipping” arises from an instability of the analytical solution upon which the distortion calculations are based, and we provide predictions of the circumstances under which pulse skipping will take place, based on a stability analysis. These predictions are confirmed by simulations
Insights into the Fallback Path of Best-Effort Hardware Transactional Memory Systems
DOI 10.1007/978-3-319-43659-3Current industry proposals for Hardware Transactional Memory (HTM) focus on best-effort solutions (BE-HTM) where hardware limits are imposed on transactions. These designs may show a significant performance degradation due
to high contention scenarios and different hardware and operating system limitations that abort transactions, e.g. cache overflows, hardware and software exceptions, etc. To deal with these events and to ensure forward progress, BE-HTM systems usually provide a software fallback path to execute a lock-based version of the code.
In this paper, we propose a hardware implementation of an irrevocability mechanism as an alternative to the software fallback path to gain insight into the hardware improvements that could enhance the execution of such a fallback. Our mechanism anticipates the abort that causes the transaction serialization, and stalls other transactions in the system so that transactional work loss is mini-
mized. In addition, we evaluate the main software fallback path approaches and propose the use of ticket locks that hold precise information of the number of transactions waiting to enter the fallback. Thus, the separation of transactional
and fallback execution can be achieved in a precise manner. The evaluation is carried out using the Simics/GEMS simulator and the complete range of STAMP transactional suite benchmarks. We obtain significant performance benefits of around twice the speedup and an abort reduction of 50% over the software fallback path for a number of benchmarks.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Artificial Symmetries for Calculating Vibrational Energies of Linear Molecules
Linear molecules usually represent a special case in rotational-vibrational calculations due to a singularity of the kinetic energy operator that arises from the rotation about the a (the principal axis of least moment of inertia, becoming the molecular axis at the linear equilibrium geometry) being undefined. Assuming the standard ro-vibrational basis functions, in the 3N−6
approach, of the form ∣∣ν1,ν2,νℓ33;J,k,m⟩
, tackling the unique difficulties of linear molecules involves constraining the vibrational and rotational functions with k=ℓ3
, which are the projections, in units of ℏ, of the corresponding angular momenta onto the molecular axis. These basis functions are assigned to irreducible representations (irreps) of the C2v
(M) molecular symmetry group. This, in turn, necessitates purpose-built codes that specifically deal with linear molecules. In the present work, we describe an alternative scheme and introduce an (artificial) group that ensures that the condition ℓ3=k
is automatically applied solely through symmetry group algebra. The advantage of such an approach is that the application of symmetry group algebra in ro-vibrational calculations is ubiquitous, and so this method can be used to enable ro-vibrational calculations of linear molecules in polyatomic codes with fairly minimal modifications. To this end, we construct a—formally infinite—artificial molecular symmetry group D∞h
(AEM), which consists of one-dimensional (non-degenerate) irreducible representations and use it to classify vibrational and rotational basis functions according to ℓ and k. This extension to non-rigorous, artificial symmetry groups is based on cyclic groups of prime-order. Opposite to the usual scenario, where the form of symmetry adapted basis sets is dictated by the symmetry group the molecule belongs to, here the symmetry group D∞h
(AEM) is built to satisfy properties for the convenience of the basis set construction and matrix elements calculations. We believe that the idea of purpose-built artificial symmetry groups can be useful in other applications
The management of subjective quality of life by short-stay hospital patients: An exploratory study
BACKGROUND: This study tested the homeostatic model of subjective quality of life in a group of 47 short stay patients as they progressed through the stages of hospitalization for surgery. METHOD: Participants completed a questionnaire measuring subjective quality of life, positive and negative affect, self-esteem, optimism and cognitive flexibility, the day prior to admission (T1), two days post-operation (T2) and one week after discharge (T3). Neuroticism and Extroversion were measured at Time 1. RESULTS: All variables remained stable across the three times, apart from positive affect, which dropped significantly post-operation but returned to its previous level post discharge. CONCLUSION: Although the homeostatic model of subjective quality of life was supported at Time 1, the analyses raise doubts about the stability of personality. This finding is consistent with recent discussions of personality
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