Design of a NURBS interpolator with minimal feed fluctuation and continuous feed modulation capability

With the growing demands to machine complex dies, moulds, aerospace, automotive, and biomedical parts in shorter cycle time, the utilization of Non-Uniform Rational B-Spline (NURBS) toolpaths has become more important than ever before. There are two challenges associated with realizing a successful NURBS trajectory generator—minimizing feedrate fluctuations and being able to modulate the feed continuously. This paper presents a robust and numerically efficient NURBS interpolation strategy. Unwanted feed fluctuations and sensitivity to round-off errors are avoided by applying the feed correction polynomial concept to NURBS toolpaths in an adaptive manner. A numerically efficient feedrate modulation strategy is developed, based on the trapezoidal acceleration profile, which guarantees that the final trajectory is jerk limited in all axes and kinematic continuity is achieved between connecting segments throughout the long toolpaths. The feed modulation strategy can be integrated with various feed optimization techniques as well. Effectiveness of the overall NURBS interpolation scheme is demonstrated in 3-axis machining of a complex sculptured surface.     

Performance of human observers and an automatic 3-dimensional computer-vision-based locomotion scoring method to detect lameness and hoof lesions in dairy cows

The objective of this study was to determine if a 3-dimensional computer vision automatic locomotion scoring (3D-ALS) method was able to outperform human observers for classifying cows as lame or nonlame and for detecting cows affected and nonaffected by specific type(s) of hoof lesion. Data collection was carried out in 2 experimental sessions (5 mo apart). In every session all cows were assessed for (1) locomotion by 2 observers (Obs1 and Obs2) and by a 3D-ALS; and (2) identification of different types of hoof lesions during hoof trimming (i.e., skin and horn lesions and combinations of skin/horn lesions and skin/hyperplasia). Performances of observers and 3D-ALS for classifying cows as lame or nonlame and for detecting cows affected or nonaffected by types of lesion were estimated using the percentage of agreement (PA), kappa coefficient (κ), sensitivity (SEN), and specificity (SPE). Observers and 3D-ALS showed similar SEN_lame values for classifying lame cows as lame (SEN_lame comparison Obs1-Obs2 = 74.2%; comparison observers-3D-ALS = 73.9–71.8%). Specificity values for classifying nonlame cows as nonlame were lower for 3D-ALS when compared with observers (SPE_nonlame comparison Obs1-Obs2 = 88.5%; comparison observers-3D-ALS = 65.3–67.8%). Accordingly, overall performance of 3D-ALS for classifying cows as lame and nonlame was lower than observers (Obs1-Obs2 comparison PA_lame/nonlame = 84.2% and κ_lame/nonlame = 0.63; observers-3D-ALS comparisons PA_lame/nonlame = 67.7–69.2% and κ_lame/nonlame = 0.33–0.36). Similarly, observers and 3D-ALS had comparable and moderate SEN_lesion values for detecting horn (SEN_lesion Obs1 = 68.6%; Obs2 = 71.4%; 3D-ALS = 75.0%) and combinations of skin/horn lesions (SEN_lesion Obs1 = 51.1%; Obs2 = 64.5%; 3D-ALS = 53.3%). The SPE_nonlesion values for detecting cows without lesions when classified as nonlame were lower for 3D-ALS than for observers (SPE_nonlesion Obs1 = 83.9%; Obs2 = 80.2%; 3D-ALS = 60.2%). This was translated into a poor overall performance of 3D-ALS for detecting cows affected and nonaffected by horn lesions (PA_{lesion/nonlesion} Obs1 = 80.6%; Obs2 = 78.3%; 3D-ALS = 63.5% and κ_{lesion/nonlesion} Obs1 = 0.48; Obs2 = 0.44; 3D-ALS = 0.25) and skin/horn lesions (PA_{lesion/nonlesion} Obs1 = 75.1%; Obs2 = 75.9%; 3D-ALS = 58.6% and κ_{lesion/nonlesion} Obs1 = 0.35; Obs2 = 0.42; 3D-ALS = 0.10), when compared with observers. Performance of observers and 3D-ALS for detecting skin lesions was poor (SEN_lesion for Obs1, Obs2, and 3D-ALS <40%). Comparable SEN_lame and SEN_lesion values for observers and 3D-ALS are explained by an overestimation of lameness by 3D-ALS when compared with observers. Thus, comparable SEN_lame and SEN_lesion were reached at the expense high number of false positives and low SPE_nonlame and SPE_nonlesion. Considering that observers and 3D-ALS showed similar performance for classifying cows as lame and for detecting horn and combinations of skin/horn lesions, the 3D-ALS could be a useful tool for supporting dairy farmers in their hoof health management.     

Routing methods for warehouses with multiple cross aisles

This paper considers routing and layout issues for parallel aisle warehouses. In such warehouses order pickers walk or drive along the aisles to pick products from storage. They can change aisles at a number of cross aisles. These cross aisles are usually located at the front and the back of the warehouse, but there can also be one or more cross aisles at positions in between. We describe a number of heuristics to determine order picking routes in a warehouse with two or more cross aisles. To analyse the performance of the heuristics, a branch-and-bound algorithm that generates shortest order picking routes is used. Performance comparisons between heuristics and the branch-and-bound algorithm are given for various warehouse layouts and order sizes. For the majority of the instances with more than two cross aisles, a newly developed heuristic appears to perform better than the existing heuristics. Furthermore, some consequences for layout are discussed. From the results it appears that the addition of cross aisles to the warehouse layout can decrease the handling time of the orders by lowering average travel times. However, adding a large number of cross aisles may increase average travel times because the space occupied by the cross aisles has to be traversed as well.     

Interference‐aware convergecast scheduling in wireless sensor/actuator networks for active airflow control applications

Emerging wireless sensor/actuator network (WSAN) technology has the potential to enable semi‐autonomous airflow control to improve the aerodynamic performance of aircraft. In this paper, a WSAN comprising of multiple linear sensor clusters terminated by actuators is proposed for active airflow control with the objective of minimizing convergecast latency. Here, the convergecast delay is defined as the time required from the beginning of a sampling period to all all sensor's data of this sampling period is received by the actuator. The objective is achieved by minimizing the separation distance of concurrent data transmission so that the number of nodes sending data in the same time slot is maximized. The problem turns into a scheduling problem with a proper selection of interference separation. However, most existing work on the scheduling in linear networks use the minimum separation of two hops to avoid collisions. This paper examines the relationship between the hop separation, signal‐to‐noise ratio, and the latency to make a selection of interference separation. A new interference aware hybrid line scheduling (HLS) algorithm is proposed and its energy consumption is analyzed. Compared with other line scheduling policies, the analysis and simulation results show that, at moderately high node densities, the proposed HLS with carefully selected hop separation is able to reduce both the delay by up to 15% and the energy consumption somehow. Copyright © 2012 John Wiley & Sons, Ltd.     

A Methodology for Architecture Exploration of Heterogeneous Signal Processing Systems

We present a methodology for the exploration of signal processing architectures at the system level. The methodology, named SPADE, provides a means to quickly build models of architectures at an abstract level, to easily map applications, modeled as Kahn Process Networks, onto these architecture models, and to analyze the performance of the resulting system by simulation. The methodology distinguishes between applications and architectures, and uses a trace-driven simulation technique for co-simulation of application models and architecture models. As a consequence, architecture models need not be functionally complete to be used for performance analysis while data dependent behavior is still handled correctly. We have used the methodology for the exploration of architectures and mappings of an MPEG-2 video decoder application.     

Effect of temperature on recrystallization behavior of cocoa butter

Crystallization of cocoa butter in the β phase directly from the melt is only possible by employing the memory effect of cocoa butter. Cocoa butter crystallized in the β phase, heated to the so-called maximal temperature (just above its melting end point), recrystallizes in the β phase after cooling to a crystallization temperature. The influence of the maximal and crystallization temperatures on the recrystallization behavior has been investigated for two cocoa butters. Rapid-starting recrystallization into the β(VI) phase and slow-starting recrystallization into the β(V) have been observed. It is concluded that rapid-starting recrystallization is induced by high-melting 1,3-distearoyl-2-oleoyl-glycerol (SOS)-rich crystals. The two β phases were identified by X-ray powder diffraction and melting ranges. However, the X-ray powder diffraction patterns for the β phases depended on the composition of the cocoa butter and on the crystallization method used. Therefore, it was not possible to take any particular β(VI) X-ray powder diffraction pattern as a standard for the β(VI) phase of all cocoa butters.     

Inference and uncertainty quantification of stochastic gene expression via synthetic models

Estimating uncertainty in model predictions is a central task in quantitative biology. Biological models at the single-cell level are intrinsically stochastic and nonlinear, creating formidable challenges for their statistical estimation which inevitably has to rely on approximations that trade accuracy for tractability. Despite intensive interest, a sweet spot in this trade-off has not been found yet. We propose a flexible procedure for uncertainty quantification in a wide class of reaction networks describing stochastic gene expression including those with feedback. The method is based on creating a tractable coarse-graining of the model that is learned from simulations, a synthetic model, to approximate the likelihood function. We demonstrate that synthetic models can substantially outperform state-of-the-art approaches on a number of non-trivial systems and datasets, yielding an accurate and computationally viable solution to uncertainty quantification in stochastic models of gene expression.     

Evaluating outcomes by means of the fair process effect: Evidence for different processes in fairness and satisfaction judgments.

The authors refine and extend their explanation of the psychology of the fair process effect (the positive influence of procedural fairness on outcome evaluations). On the basis of fairness heuristic theory's substitutability proposition, the authors predicted and found that outcome evaluations show strong effects of procedural fairness when outcomes are better or worse than expected, whereas less strong fair process effects appear when outcomes are equal to or differ from the outcome of a comparison other. This finding suggests some important differences in how people use expectations versus social comparisons as reference points for evaluating outcomes. Findings also revealed that fairness judgments do not always show the same effects as do satisfaction judgments, indicating differences in the way people form judgments on these two dimensions of outcome evaluation. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

A Venturi Suction Electrode Array for Clinical Body Surface Mapping

In order to extend the clinical use of body surface mapping, we developed an efficient lead system which can be used under intensive care circumstances. The array consists of flexible straps with electrodes which are sucked onto the thorax by running pressurized air through venturi ejectors. Major features are: rapid application and removal, high reliability, easy handling, and suitability for repeated use with minimal discomfort to the patient.