Accelerated testing of on‐board diagnostics

Modern products frequently feature monitors designed to detect actual or impending malfunctions. False alarms (Type I errors) or excessive delays in detecting real malfunctions (Type II errors) can seriously reduce monitor utility. Sound engineering practice includes physical evaluation of error rates. Type II error rates are relatively easy to evaluate empirically. However, adequate evaluation of a low Type I error rate is difficult without using accelerated testing concepts, inducing false alarms using artificially low thresholds and then selecting production thresholds by appropriate extrapolation, as outlined here. This acceleration methodology allows for informed determination of detection thresholds and confidence in monitor performance with substantial reductions over current alternatives in time and cost required for monitor development. Copyright © 2006 John Wiley & Sons, Ltd.     

NICE h : a higher-order explicit numerical scheme for integration of constitutive models in plasticity

The article introduces, as a result of further development of the first-order scheme NICE, a simple and efficient higher-order explicit numerical scheme for the integration of a system of ordinary differential equations which is constrained by an algebraic condition (DAE). The scheme is based on the truncated Taylor expansion of the constraint equation with order h of the scheme being determined by the highest exponent in the truncated Taylor series. The integration scheme thus conceived will be named NICE ^h , considering both principal premises of its construction. In conjunction with a direct solution technique used to solve the boundary value problem, the NICE ^h scheme is very convenient for integrating constitutive models in plasticity. The plasticity models are defined mostly by a system of algebraic and differential equations in which the yield criterion represents the constraint condition. To study the properties of the new integration scheme, which, like the forward-Euler scheme, is characterised by its implementation simplicity due to the explicitness of its formulations, a damage constitutive model (Gurson–Tvergaard–Needleman model) is considered. The general opinion that the implicit backward-Euler scheme is much more accurate than the thus-far known explicit schemes is challenged by the introduction of the NICE ^h scheme. The accuracy of the higher-order explicit scheme in the studied cases is significantly higher than the accuracy of the classical backward-Euler scheme, if we compare them under the condition of a similar CPU time consumption.     

Adaptive atomic capture of multiple molecules

Facing the scale, heterogeneity and dynamics of the global computing platform emerging on top of the Internet, autonomic computing has been raised recently as one of the top challenges of computer science research. Such a paradigm calls for alternative programming abstractions, able to express autonomic behaviours. In this quest, nature-inspired analogies regained a lot of interest. More specifically, the chemical programming paradigm, which envisions a program’s execution as a succession of reactions between molecules representing data to produce a result, has been shown to provide some adequate abstractions for the high-level specification of autonomic systems.     

Neural network Reinforcement Learning for visual control of robot manipulators

It is known that most of the key problems in visual servo control of robots are related to the performance analysis of the system considering measurement and modeling errors. In this paper, the development and performance evaluation of a novel intelligent visual servo controller for a robot manipulator using neural network Reinforcement Learning is presented. By implementing machine learning techniques into the vision based control scheme, the robot is enabled to improve its performance online and to adapt to the changing conditions in the environment. Two different temporal difference algorithms (Q-learning and SARSA) coupled with neural networks are developed and tested through different visual control scenarios. A database of representative learning samples is employed so as to speed up the convergence of the neural network and real-time learning of robot behavior. Moreover, the visual servoing task is divided into two steps in order to ensure the visibility of the features: in the first step centering behavior of the robot is conducted using neural network Reinforcement Learning controller, while the second step involves switching control between the traditional Image Based Visual Servoing and the neural network Reinforcement Learning for enabling approaching behavior of the manipulator. The correction in robot motion is achieved with the definition of the areas of interest for the image features independently in both control steps. Various simulations are developed in order to present the robustness of the developed system regarding calibration error, modeling error, and image noise. In addition, a comparison with the traditional Image Based Visual Servoing is presented. Real world experiments on a robot manipulator with the low cost vision system demonstrate the effectiveness of the proposed approach.     

The ELPI Response and Data Reduction II: Properties of Kernels and Data Inversion

The first part of this article reports the analytical form of the Electrical Low Pressure Impactor (ELPI) kernel functions. In this latter part, the numerical quality of ELPI response matrices is studied and an example of an inversion algorithm is given. The ELPI assemblies with and without an electrical filter stage and with smooth or sintered impaction plates are studied and compared with basic impactor kernels and the kernels for the calculation of the aerosol mass distribution. It is shown that the ELPI assembly with the electrical filter stage and smooth impaction plates should be the best choice for the inversion of data if no bounce occurs. The comparison to a mass impactor shows that the devices are on par in data inversion. The inversion ELPI data is studied with a Bayesian algorithm assuming a bimodal lognormal size distribution of the aerosol. The algorithm includes a novel procedure for obtaining an initial guess of the distribution parameters. To our knowledge, it is also the first algorithm to use ELPI current readings as its input. Simulations and diesel emission measurements show that the proposed algorithm is a useful tool in the study of ELPI data.     

Sonar detection and measurement of ice in a freezing river II: Observations and results on frazil ice

Results from 2004-2008 BC Hydro SWIPS (Shallow Water Ice Profiling Sonar) monitoring programs on the Peace River are presented and analyzed with respect to their content of information on the properties and behaviour of frazil ice suspended in water column. Strong distinctions were made in analyses applied to data collected, respectively, prior to and following local stabilization of the seasonal ice cover. This choice is shown to reflect both the behaviour and origins of the frazil ice present in these two intervals. Pre-freeze-up frazil tends to coat submerged surfaces, grows rapidly while in suspension and is only rarely and episodically present. It shows time dependences quite different from those associated with frazil detected prior to freeze-up. Frazil under a stationary ice cover is ubiquitous, does not adhere to other materials and appears to closely associated with the ice cover undersurface. The return intensity profiles observed in pre-freeze-up frazil events increased roughly linearly with height in the water column. Profile comparisons with earlier simulation results allowed inferences on particle size distributions and their controlling processes. The bulk of data analysis efforts was devoted to clarifying the time dependences of the more abundant post-stabilization SWIPS intensity data and its underlying connections to changes in the major river, atmosphere and ice cover environmental parameters. The obtained results showed unlagged or weakly negatively-lagged, positive correlations between such intensities and both river water levels and air temperatures (or solar radiation input) on, at least, diurnal and shorter time scales. The water level parameter was the stronger of these two influences and was believed to be representative of a physical link to river flow speed. Lower frequency connections to the physical state of the ice cover were also apparent. Interpretations of these results were offered in terms of a local equilibrium between the suspended frazil population and a dynamic slush layer at the bottom of the ice cover. Initial steps were taken toward developing and testing analysis tools potentially capable of supporting combined analysis and modelling of this equilibrium. A simple interpretative approach was applied to data acquired at a single acoustic frequency based upon combined use of a Rouse Law-based Inverted sediment model of uniformly-sized spherical frazil particles and volume backscattering coefficients measured in post-freeze-up intervals. Results suggested consistency with the basic form of return intensity profiles at most but not all times. For suitable measurement periods, the approach yielded reasonable estimates of the major particle size and concentration parameters. The deficiencies of this approach are discussed and compared with expectations and results from recently successful simultaneous measurements at two acoustic frequencies. Priorities are identified for validation, and refinement of single and multifrequency approaches along with integrated study of the lower ice cover as part of a broader program to understand frazil ice growth in freezing rivers.     

Fabrication of diamond nanowires for quantum information processing applications

We present a design and a top-down fabrication method for realizing diamond nanowires in both bulk single crystal and polycrystalline diamond. Numerical modeling was used to study coupling between a Nitrogen Vacancy (NV) color center and optical modes of a nanowire, and to find an optimal range of nanowire diameters that allows for large collection efficiency of emitted photons. Inductively coupled plasma (ICP) reactive ion etching (RIE) with oxygen is used to fabricate the nanowires. Drop-casted nanoparticles (including Au, SiO₂ and Al₂O₃) as well as electron beam lithography defined spin-on glass and evaporated Au have been used as an etch mask. We found Al₂O₃ nanoparticles to be the most etch resistant. At the same time FOx e-beam resist (spin-on glass) proved to be a suitable etch mask for fabrication of ordered arrays of diamond nanowires. We were able to obtain nanowires with near-vertical sidewalls in both polycrystalline and single crystal diamond. The heights and diameters of the polycrystalline nanowires presented in this paper are ≈ 1 μm and 120–340 nm, respectively, having a 200 nm/min etch rate. In the case of single crystal diamond (types Ib and IIa) nanowires the height and diameter for different diamonds and masks shown in this paper were 1–2.4 μm and 120–490 nm with etch rates between 190 and 240 nm/min.     

Estimation of the number of trays for natural gas triethylene glycol dehydration column

The paper deals with the tray-to-tray method for determining the required number of trays in columns with intensive entrainment of liquid when the operating line of the “dry working regime” is not straight and with a small concentration of diffusing component in gas. Presented calculations show that the number of transfer units for gas and liquid should be calculated using the AIChE method accompanied with longitudinal mixing according to Gilbert properly transformed for case of diffusion through stagnant film. The suggested method can be applied for TEG dehydration absorbers-columns for dehydration of natural gas using triethylene glycol with system factor SF = 0.5.