Vision‐based terrain characterization and traversability assessment

This article presents novel techniques for real‐time terrain characterization and assessment of terrain traversability for a field mobile robot using a vision system and artificial neural networks. The key terrain traversability characteristics are identified as roughness, slope, discontinuity, and hardness. These characteristics are extracted from imagery data obtained from cameras mounted on the robot and are represented in a fuzzy logic framework using perceptual, linguistic fuzzy sets. The approach adopted is highly robust and tolerant to imprecision and uncertainty inherent in sensing and perception of natural environments. The four traversability characteristics are combined to form a single Fuzzy Traversability Index, which quantifies the ease‐of‐traversal of the terrain by the mobile robot. Experimental results are presented to demonstrate the capability of the proposed approach for classification of different terrain segments based on their traversability. © 2001 John Wiley & Sons, Inc.     

Interoperability and Electronic Commerce: A New Policy Framework for Evaluating Strategic Options

Enthusiasm for the anticipated social dividends of the Internet appears boundless. Indeed, the Internet is expected to do no less than virtually transform society. Yet even as the Internet races ambitiously toward critical mass, some social scientists are beginning to examine carefully the policy implications of current demographic patterns of Internet access and usage. Key demographic variables like income and education drive the policy questions surrounding the Internet because they are the most likely have a differential impact on the consequences of interactive electronic media for different segments in our society. Given these concerns, we set out to conduct a systematic investigation of the differences between whites and African Americans in the United States with respect to computer access, the primary current prerequisite for Internet access, and Web use. We wished to examine whether observed race differences in access and use can be accounted for by differences in income and education, how access influences use, and when race matters in the calculus of equal access. The particular emphasis of this research is on how such differences may be changing over time. We believe our results may be used as a window through which policymakers might view the job of ensuring access to the Internet for the next generation.     

Vascular dementia: dead or alive?

Allergic respiratory inflammation in target organs does not occur in any atopic (genetically susceptible) subject, since other not fully characterized factors can influence the subsequent development of overt clinical disease. Here are presented some recent developments in experimental animal and human research that can offer a new "non-classical" interpretation about the way by which allergens are recognized and allergic inflammation persists. These aspects of the immunopathogenesis of allergic diseases can now be viewed as organ-specific pathways, acting independently from other peripheral lymphoid organs. This is a consequence of new knowledge about the function of, and molecular interactions by, intraepithelial gammadelta T cells and CD1+ dendritic cells. The allergic subject, unlike the normal one, is equipped at the mucosal surface by particular T cell and antigen-presenting cell (APC) subsets that enable them to recognize undenatured proteic and non-proteic (glycolipidic) external structures of aerodispersed particles, presented in the context of CD1 molecules. Once initiated, the mucosal allergic reaction cannot be turned off in atopic individuals because CD4+ allergen-specific T cells lack surface Fas receptor. This defect, that impairs the so-called activation-induced programmed cell death (determined by Fas/FasL interaction), is caused by the local Th2-type cytokine milieu.     

Fixed-time sliding mode observer-based controller for a class of uncertain nonlinear double integrator systems

This paper investigates a fixed-time convergence issue using the sliding mode observer-based controller for a class of uncertain nonlinear double integrator systems. This observer-based controller is designed assuming that only the first state measurement is available and there is no information about external disturbances and modeling uncertainties. A new form of sliding mode observer in combination with a sliding mode controller is designed to estimate unmeasured state and unknown disturbances and uncertainties as well as provide the estimated data in the control law. A novel form of sliding surfaces for the robust observer-based controller is proposed for which fixed-time convergence is guaranteed to achieve trajectory tracking. In the proposed fixed-time scheme, the bound on the settling time is user-defined using design parameters regardless of the system's initial conditions. The control law and observer law are designed such that the chattering issue is alleviated in the control signal. The stability analysis of the closed-loop system using the observer-based controller is established via the Lyapunov theory. The validity of the controller design is tested by applying and simulating an example of a robot manipulator in Simulink/MATLAB. The superiority of the proposed method is demonstrated by comparing it with two other methods from the relevant literature.     

Politics and Science: A Combustible Mixture. Comment.

Comments on the article by Crosby et al (see record 2003-03405-003) in which psychological research is brought to bear on an examination of the policy of affirmative action. In their article, Crosby and colleagues cite the current author's paper "The Role of Value in the World of Psychology" (1999; see record 1999-11644-004) to support their contention that "science can never be fully free of values". The current author states that Crosby and colleagues misinterpreted his position. Specifically, the author believes that the question of whether science is value-loaded or value-free is pointless because the scientific enterprise consists of a variety of independent activities. Discussion centers on the implications of the fact/value dichotomy, science and politics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adaptive coordination in cardiac anaesthesia: a study of situational changes in coordination patterns using a new observation system

Patient care in hospital settings requires coordinated team performance. Studies in other industries show that successful teams adapt their coordination processes to the situational task requirements. This prospective field study aimed to test a new observation system and investigate patterns of adaptive coordination within operating room teams. A trained observer recorded coordination activities during 24 cardiac surgery procedures. The study tested whether different patterns occur during different phases of and between different types of surgical procedures (two-way multivariate ANOVA with repeated measure). A statistically significant increase was found in clinical and coordination activities in phases of the operation with high task interdependence. The highest level of 'coordination via the work environment' (i.e. an implicit coordination mechanism) was recorded during the actual procedure on the beating heart. These findings prove the sensitivity of the observation system developed and evaluated in this study and provide insight into patterns of adaptive coordination in cardiac anaesthesia. This study furthers our understanding of adaptive coordination as a cornerstone of effective team performance in complex work environments. Using a new observation system, it describes patterns employed by health care professionals in response to changing task demands in an acute patient care setting.     

A hybrid Branch-and-Bound and evolutionary approach for allocating strings of applications to heterogeneous distributed computing systems

Providing efficient workload management is an important issue for a large-scale heterogeneous distributed computing environment where a set of periodic applications is executed. The considered shipboard distributed system is expected to operate in an environment where the input workload is likely to change unpredictably, possibly invalidating a resource allocation that was based on the initial workload estimate. The tasks consist of multiple strings, each made up of an ordered sequence of applications. There is a quality of service (QoS) minimum throughput constraint that must be satisfied for each application in a string, and a maximum utilization constraint that must be satisfied on each of the hardware resources in the system. The challenge, therefore, is to efficiently and robustly manage both computation and communication resources in this unpredictable environment to achieve high performance while satisfying the imposed constraints. This work addresses the problem of finding a robust initial allocation of resources to strings of applications that is able to absorb some level of unknown input workload increase without rescheduling. The proposed hybrid two-stage method of finding a near-optimal allocation of resources incorporates two specially designed mapping techniques: (1) the Permutation Space Genitor-Based heuristic, and (2) the follow-up Branch-and-Bound heuristic based on an Integer Linear Programming (ILP) problem formulation. The performance of the proposed resource allocation method is evaluated under different simulation scenarios and compared to an iteratively computed upper bound.     

Thermodynamic properties of the liquid Sn−Ge and Sn−Au systems by mass spectrometry

The activities and partial molar heats of mixing have been determined for the liquid Sn?Ge system at 1773 K and the liquid Sn?Au system at 1873 K. The experimental technique consisted of analyzing Knudsen cell effusates with a TOF mass spectrometer. The ion current ratios for the monomeric vapor species were measured as a function of temperature and composition and the thermodynamic properties calculated using a modified form of the Gibbs-Duhem equations. In addition to exhibiting very slight positive deviation from ideal behavior, the Sn?Ge system displayed parabolic solution behavior over the entire composition range. The results for the excess partial molar free energies and partial molar heats of mixing for the Sn?Ge system can be represented by $$G_1^E = 3.06X_2^2 kJ/g \cdot mol$$ and $$H_1^M = 5.86X_2^2 kJ/g \cdot mol$$ at 1773 K. The Sn?Au system exhibited negative deviation from ideal behavior and the results can be partially represented by $$\begin{gathered} \log _{10} \gamma Au = - 0.388 - 0.650 X_{Sn}^2 (0.00 \leqslant X_{Au} \leqslant 0.30) \hfill \\ \log _{10} \gamma Sn = 0.658 - 2.63 X_{Au}^2 (0.00 \leqslant X_{Sn} \leqslant 0.25) \hfill \\ \end{gathered} $$ and $$H_1^M = - 61.7 X_2^2 kJ/g \cdot mol$$ at 1873 K. Comparison of the results with other investigations indicates the heat of mixing for the system becomes more exothermic with increasing temperature above 1100 K. An experimental technique is presented for determining the effect of dissociative ionization of molecular species on the activity coefficient. The effect of dissociative ionization of the molecular species present in the Knudsen cell effusate was determined to be negligible.     

Sufficient and necessary conditions: Misused terms.

Notes that although the terms sufficient and necessary are absolute in nature and allow no counterexamples, psychologists inappropriately apply them to probabilistic outcomes. Misuse of the terms leads to confusion and the creation of pseudoissues, as illustrated in the argument over whether therapist warmth is a necessary or sufficient condition in behavioral desensitization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterization of the iterative application of makespan heuristics on non-makespan machines in a heterogeneous parallel and distributed environment

Heterogeneous computing (HC) is the coordinated use of different types of machines, and networks to process a diverse workload in a manner that will maximize the combined performance and/or cost effectiveness of the system. Heuristics for allocating resources in an HC system are based on some optimization criterion. A common optimization criterion is to minimize the completion time of the machine that finishes last (makespan). In this study, we consider an iterative approach that repeatedly runs a mapping heuristic to minimize the makespan of the considered machines and tasks. For each successive iteration, the makespan machine of the previous iteration and the tasks assigned to it are removed from the set of considered machines and tasks. This study focuses on understanding the different mathematical characteristics of resource allocation heuristics that cause them to behave differently when combined with this iterative approach. This paper has three main contributions. The first contribution is the study of an iterative technique used in conjunction with resource allocation heuristics. The second contribution is the definition and mathematical characterization of “iteration invariant” heuristics. The third contribution is to determine the characteristics of a heuristic that will cause the mapping to change across iterations.