Undesired Configurations Research Articles

Context-Aware Adaptive Applications: Fault Patterns and Their Automated Identification

Applications running on mobile devices are intensely context-aware and adaptive. Streams of context values continuously drive these applications, making them very powerful but, at the same time, susceptible to undesired configurations. Such configurations are not easily exposed by existing validation techniques, thereby leading to new analysis and testing challenges. In this paper, we address some of these challenges by defining and applying a new model of adaptive behavior called an Adaptation Finite-State Machine (A-FSM) to enable the detection of faults caused by both erroneous adaptation logic and asynchronous updating of context information, with the latter leading to inconsistencies between the external physical context and its internal representation within an application. We identify a number of adaptation fault patterns, each describing a class of faulty behaviors. Finally, we describe three classes of algorithms to detect such faults automatically via analysis of the A-FSM. We evaluate our approach and the trade-offs between the classes of algorithms on a set of synthetically generated Context-Aware Adaptive Applications (CAAAs) and on a simple but realistic application in which a cell phone's configuration profile changes automatically as a result of changes to the user's location, speed, and surrounding environment. Our evaluation describes the faults our algorithms are able to detect and compares the algorithms in terms of their performance and storage requirements.

A Heuristic Approach for Constrained Real Time Motion Planning of a Redundant 7-DOF Mechanism for 3D Laser Scanning

This article presents a heuristic algorithm for motion planning of a short range 7-DOF Laser Scanning System consisting of a 6-DOF vertical robot arm and a rotary table holding the workpiece. The redundancy of the mechanism is exploited for specifying certain constraints such as imposing a smooth motion of the rotary table while respecting the acceleration and speed limits and avoiding undesirable configurations of the robot arm such as the kinematic singularities, out-of-range conditions and collisions between the mechanical elements of the system (robot, table, workpiece and laser probe). The paper also presents the control system of the rotary table, and a communication protocol which allows the integration of the above-mentioned planning algorithm into the 3D scanning system.

Local or Global Minima: Flexible Dual-Front Active Contours

Most variational active contour models are designed to find local minima of data-dependent energy functionals with the hope that reasonable initial placement of the active contour will drive it toward a "desirable" local minimum as opposed to an undesirable configuration due to noise or complex image structure. As such, there has been much research into the design of complex region-based energy functionals that are less likely to yield undesirable local minima when compared to simpler edge-based energy functionals whose sensitivity to noise and texture is significantly worse. Unfortunately, most of these more "robust" region-based energy functionals are applicable to a much narrower class of imagery compared to typical edge-based energies due to stronger global assumptions about the underlying image data. Devising new implementation algorithms for active contours that attempt to capture more global minimizers of already proposed image-based energies would allow us to choose an energy that makes sense for a particular class of energy without concern over its sensitivity to local minima. Such implementations have been proposed for capturing global minima. However, sometimes the completely-global minimum is just as undesirable as a minimum that is too local. In this paper, we propose a novel, fast, and flexible dual front implementation of active contours, motivated by minimal path techniques and utilizing fast sweeping algorithms, which is easily manipulated to yield minima with variable "degrees" of localness and globalness. By simply adjusting the size of active regions, the ability to gracefully move from capturing minima that are more local (according to the initial placement of the active contour/surface) to minima that are more global allows this model to more easily obtain "desirable" minimizers (which often are neither the most local nor the most global). Experiments on various 2D and 3D images and comparisons with some active contour models and region-growing methods are also given to illustrate the properties of this model and its performance in a variety of segmentation applications.

Direct kinematic analysis of a 3-PRS parallel mechanism

This paper presents the direct kinematics solutions for a novel 3-PRS parallel mechanism. The geometric method is applied to formulate three coupled trigonometric equations. One algorithm for solving the three coupled equations is to use the Bezout’s elimination method which leads to a total of 64 solutions. By categorizing the 64 solutions into six groups and further examining the corresponding configuration for each group, the preferred solution to the direct kinematics problem can be obtained. The other approach for solving the coupled equations is to apply the optimization techniques with side and behavior constraints set by analyzing undesired configurations. This approach can obtain the preferred solution without checking all the possible solutions. Moreover, it can perform more efficiently than the elimination method.

Evaluation of axial and flexural stresses in the vertebral body cortex and trabecular bone in lordosis and two sagittal cervical translation configurations with an elliptical shell model

Background: Osteoarthritis and spinal degeneration are factors in neck and back pain. Calculations of stress in clinically occurring configurations of the sagittal cervical spine are rare. Objective: To calculate and compare combined axial and flexural stresses in lordosis versus cervical configurations in anterior and vertical sagittal head translated positions. Design: Digitized measurements from lateral cervical radiographs of 3 different shapes were used to calculate axial loads and bending moments on the vertebral bodies of C2-C7. Methods: An elliptical shell model was used to model horizontal cross-sections of the vertebral bodies of C2 through T1. Axial and flexural stresses were calculated with short compression block equations. Elliptical shell modeling permitted separation of stresses into cortical and inner medullary regions. Digitized radiographic points were used to create polynomials representing the shape of the sagittal cervical curvatures from C1 to T1. To calculate bending moments at each vertebral segment, moment arms from a vertical line through C1 were determined from digitizing. Results: Compared with the normal lordosis, stresses on the anterior vertebral body cortical margins of C5-T1 in the sagittal translated postures are compression rather than tension. At the posterior vertebral bodies in the anteriorly translated position and vertically translated postures, the stresses change from compression to tension at C5 through T1. In absolute value (ABS) compared with values at the same segments in a normal lordosis, the magnitude of the combined anterior stresses in the sagittal postures are higher at C5-C7 (eg, ABS[σstraight/σnormal] ≃ 1.25 to 4.25). Conclusions: Vertebral body stresses are reversed in direction at C5-T1 in sagittal translated postures compared to a normal lordosis. Stress analysis, with implications for bone remodeling, indicates that both sagittal head translation postures, anterior head carriage, and vertical head translation, are undesirable configurations in the cervical spine. (J Manipulative Physiol Ther 2002;25:391-401)

Comparison of axial and flexural stresses in lordosis and three buckled configurations of the cervical spine

Objective. To calculate and compare combined axial and flexural stresses in lordosis versus buckled configurations of the sagittal cervical curve. Design. Digitized measurements from lateral cervical radiographs of four different shapes were used to calculate axial loads and bending moments on the vertebral bodies of C2–C7. Background. Osteoarthritis and spinal degeneration are factors in neck and back pain. Calculations of stress in clinically occurring configurations of the sagittal cervical spine are rare. Methods. Center of gravity of the head (inferior–posterior sella turcica) and vertebral body margins were digitized on four different lateral cervical radiographs: lordosis, kyphosis, and two “S”-shapes. Polynomials (seventh degree) and stress concentrations on the concave and convex margins were derived for the shape of the sagittal cervical curvatures from C1 to T1. Moments of inertia were determined from digitizing and the use of an elliptical shell model of cross-section. Moment arms from a vertical line through the center of gravity of the head to the atlas and scaled neck extensor moment arms from the literature were used to compute the vertical component of extensor muscle effort. Segmental lever arms were calculated from a vertical line through C1 to each vertebra. Results. In lordosis, anterior and posterior stresses in the vertebral body are nearly uniform and minimal. In kyphotic areas, combined stresses changed from tension to compression at the anterior vertebral margins and were very large (6–10 times as large in magnitude) compared to lordosis. In kyphotic areas at the posterior vertebral body, the combined stresses changed from compression (in lordosis) to tension. Conclusions. The stresses in kyphotic areas are very large and opposite in direction compared to a normal lordosis. This analysis provides the basis for the formation of osteophytes (Wolff's Law) on the anterior margins of vertebrae in kyphotic regions of the sagittal cervical curve. This indicates that any kyphosis is an undesirable configuration in the cervical spine. Relevance Osteophytes and osteoarthritis are found at areas of altered stress and strain. Axial and flexural stresses at kyphotic areas in the sagittal cervical spine are abnormally high.

Optimal conditions for inverse kinematics of a robot manipulator with redundancy

SummaryThe algorithms of inverse kinematics based on optimality constraints have some problems because those are based only on necessary conditions for optimality. One of the problems is a switching problem, i.e., an undesirable configuration change from a maximum value of a performance measure to a minimum value may occur and cause an inverse kinematic solution to be unstable. In this paper, we derive sufficient conditions for the optimal solution of the kinematic control of a redundant manipulator. In particular, we obtain the explicit forms of the switching condition for the optimality constraintsbased methods. We also show that the configuration at which switching occurs is equivalent to an algorithmic singularity in the extended Jacobian method. Through a numerical example of a cyclic task, we show the problems of the optimality constraints-based methods. To obtain good configurations without switching and kinematical singularities, we propose a simple algorithm of inverse kinematics.

The Workspace of a General Geometry Planar Three-Degree-of-Freedom Platform-Type Manipulator

This paper focuses on the direct workspace problems of a general geometry fully-parallel-actuated, planar three-degree-of-freedom platform-type manipulator. A set of equations are presented that determine the workspace as a function of the platform orientation. The formulation is governed by the solution to the inverse position problem of the manipulator. The reachable positions of the end-effector point, for a specified platform orientation, are analyzed. To illustrate the concepts, a practical example is included where the end-effector is required to move a cup filled with water. Then the platform orientation, for a specified location of the end-effector point, is studied. If an arbitrary orientation is possible, the specified location of the end-effector point is said to be within the primary workspace. The paper includes a detailed discussion of the total primary workspaces of the manipulator. The approach adopted here is to regard the manipulator as a combination of three planar, three-revolute open chains. For the sake of completeness, the influence of special manipulator geometry on the workspace is also discussed. Finally, the paper includes the conditions that cause stationary configurations of the manipulator. Insight into these undesirable configurations is provided by a study of the location of the absolute instant center of the platform.

General approach for the synthesis of polyquinenes via the Weiss reaction XV. Synthesis of the [5.5.5.5]fenestrane system via the aldol approach and studies directed toward the [5.5.6.6]fenestranes

The all cis-8a, 12b-diacetoxytetracyclo[5.5.1.0. 4,130 10,13]tridecane-2,6-dione 9 was successfully synthesized via aldolization of the diketodialdehyde 8 under conditions of equilibration, followed by trapping with acetic anhydride. Aldol cyclization of the dialdehyde 14 to provide the [5.5.6.6]fenestrane system 12 was also attempted. This resulted in the observation of tetracycle 25 with the desired ring system albeit as a minor product. The major products isolated from this approach were the undesired α,β-unsaturated aldehyde 22 and monoaldehyde 23, the latter of which contained a configuration opposite to that of C-5 in 12. In addition, the related bisacylation approach provided 26 as the major product with the undesired configuration at C-8. This cyclization furnished the transannular tetraone 27 at higher temperature.

The Effect of Electrode Placement and Finite Matrix Conductivity on the Performance of Flow‐Through Porous Electrodes

A one‐dimensional model for flow‐through porous electrodes is used to predict the effluent concentration as a function of matrix conductivity and electrode length for upstream and downstream placement of the counterelectrode and current collector relative to the fluid inlet to the working electrode. Two chemical systems are considered: (i) the removal of copper from sulfate solutions, and (ii) the removal of silver from thiosulfate solutions. For an infinite matrix conductivity, the lowest effluent concentration is achieved when the counterelectrode is placed upstream to the fluid inlet of the working electrode. When the matrix conductivity is small, the lowest effluent concentration is still achieved for upstream placement of the counterelectrode; however, the optimum placement of the current collector depends on the chemical system and the value of the matrix conductivity that can be achieved in practice. Calculations show that for downstream placement of the counterelectrode a limiting current distribution cannot be achieved (for electrode lengths of interest here). The most undesirable configuration for achieving a low effluent concentration when the matrix conductivity is low is when both the counterelectrode and current collector are placed downstream of the fluid inlet. Distribution of potential, reaction rate, and electric driving force are presented for four different configurations: (i) upstream counterelectrode, downstream current collector, (ii) downstream counterelectrode, upstream current collector, (iii) upstream counterelectrode, upstream current collector, and (iv) downstream counterelectrode, downstream current collector.