Computation of stationary points of distance functions

This paper presents an algorithm for computation of the stationary points of the squared distance functions between two point sets. One point set consists of a single space point, a rational B-spline curve, or a rational B-spline surface. The problem is reformulated in terms of solution of n polynomial equations with n variables expressed in the tensor product Bernstein basis. The solution method is based on subdivision relying on the convex hull property of the n-dimensional Bernstein basis and minimization techniques. We also cover classification of the stationary points of these distance functions, and include a method for tracing curves of stationary points in case the solution set is not zerodimensional. The distance computation problem is shown to be equivalent to the geometrically intuitive problem of computing collinear normal points. Finally, examples illustrate the applicability of the method     

Estimating burn severity from Landsat dNBR and RdNBR indices across western Canada

National parks in western Canada experience wildland fire events at differing frequencies, intensities, and burn severities. These episodic disturbances have varying implications for various biotic and abiotic processes and patterns. To predict burn severity, the differenced Normalized Burn Ratio (dNBR) algorithm, derived from Landsat imagery, has been used extensively throughout the wildland fire community. In Canada, few accuracy assessments have been undertaken to compare the accuracy of the dNBR algorithm to its relative form (RdNBR). To investigate the accuracies of these two algorithms in Canada's National Parks, we hypothesized that RdNBR would outperform dNBR in two specific applications based on former research by Miller and Thode (2007). The first was the capacity of the RdNBR to produce more accurate results than dNBR over a wide range of fires and secondly in pre-fire landscapes with low canopy closure and high heterogeneity. To investigate these questions, dNBR and RdNBR indices were extracted from Landsat imagery and compared to the measurements of the Composite Burn Index (Key & Benson, 2006). Following this, best fit models were developed and statistically tested at the individual, regional, overall, and vegetative levels. We then developed confusion matrices to assess the relative strength and weakness of each model. As an additional means of comparing model accuracy, we tested Hall et al.'s (2008) non-linear model in estimating burn severity for the study's western boreal region and individual fires. The results indicate that across all fires, the RdNBR-derived model did not estimate burn severity more accurately than dNBR (65.2% versus 70.2% classification accuracy, respectively) nor in the heterogeneous and low canopy cover landscapes. In addition, we conclude that RdNBR is no more effective than dNBR at the regional, individual, and fine-scale vegetation levels. The Hall et al. (2008) model was found to estimate burn severity in the western boreal region with a higher overall kappa than both the dNBR and RdNBR study models. The results herein support the continued research and pursuit of developing regional remote sensing derived models in western Canada.     

Essential design and fabrication considerations for the reliable performance of an electrothermal MEMS microgripper

Microsystem Technologies - Over the past years, microelectromechanical systems (MEMS) have become a vital component within a wide range of technologies, making the study of their performance and...     

直面客户互联体验的新现实

<正>为了提供多重体验,企业需要创建适用于所有模式的应用,为每个客户提供个性化体验,且在不受任何互动的影响下,将后端一致性融入核心生态系统。因此,企业必须考虑如何使AR和VR技术在其数字化进程中发挥作用。随着互联网的发展,客户与品牌的互动渠道越来越多。世界每时每刻都在由物理化向数字化方向发展,而虚拟现实（VR）和增强现实（A R）等新兴技术的发展强化了这一转变。如今,良好的客户体验并非仅靠移动应用、稳定的网站或强大的服务产品就可以实现。     

A Stable Switched-System Approach to Collision-Free Wheeled Mobile Robot Navigation

This paper presents a novel switched-system approach for obstacle avoidance by mobile robots. This approach does not suffer from common drawbacks of existing methods, such as needing prior knowledge of obstacles, or local minima or chattering in control laws. We define an attractive and an avoidance vector in obstacle-free and obstacle-avoidance regions, respectively. Next, we define an unified velocity vector, which represents either the attractive vector or the avoidance vector, and drives the robot away from the obstacle and ultimately towards the goal. The avoidance vector differs from the repulsive vector commonly used in potential field approaches, rather it is defined always perpendicular to such a repulsive vector and projects positively onto the attractive vector. The unified velocity vector enables the use of a common Lyapunov function in analyzing the stability of the system under arbitrary switching. Novel switching rules are proposed for obstacles that can be well bounded by a circle in the local subset of SE(2). To better handle large, non-circular obstacles, a separate switching signal is proposed. Through the choice of switching rule, we investigate the chattering problem that can hinder some switching controllers. We present two control laws, one with bounded inputs and one with no bounds on inputs. We prove both control schemes are asymptotically stable and guide the robot to the goal while avoiding obstacles. To verify the effectiveness of the proposed approach, as well as compare the control laws and switching rules, several simulations and experiments have been conducted.     

General schema theory for genetic programming with subtree-swapping crossover: Part II

This paper is the second part of a two-part paper which introduces a general schema theory for genetic programming (GP) with subtree-swapping crossover (Part I (Poli and McPhee, 2003)). Like other recent GP schema theory results, the theory gives an exact formulation (rather than a lower bound) for the expected number of instances of a schema at the next generation. The theory is based on a Cartesian node reference system, introduced in Part I, and on the notion of a variable-arity hyperschema, introduced here, which generalises previous definitions of a schema. The theory includes two main theorems describing the propagation of GP schemata: a microscopic and a macroscopic schema theorem. The microscopic version is applicable to crossover operators which replace a subtree in one parent with a subtree from the other parent to produce the offspring. Therefore, this theorem is applicable to Koza's GP crossover with and without uniform selection of the crossover points, as well as one-point crossover, size-fair crossover, strongly-typed GP crossover, context-preserving crossover and many others. The macroscopic version is applicable to crossover operators in which the probability of selecting any two crossover points in the parents depends only on the parents' size and shape. In the paper we provide examples, we show how the theory can be specialised to specific crossover operators and we illustrate how it can be used to derive other general results. These include an exact definition of effective fitness and a size-evolution equation for GP with subtree-swapping crossover.     

Nonassertiveness, dysfunctional attitudes, and mild levels of depression.

Studied the relationships between nonassertion, dysfunctional attitudes, and mild levels of depression, using 89 undergraduates who completed 2 self-report measures of assertion, the Beck Depression Inventory and the Dysfunctional Attitudes Scale (DAS). In accord with past research, it was found that assertion deficits increased significantly with increases in depression scores. The presence of dysfunctional attitudes also accounted for a significant increase in assertion difficulties, over and above that accounted for by depression. In particular, Ss scoring high on the DAS indicated greater difficulty in the resolution of interpersonal conflicts and the comfortable assertion of their own rights, compared to Ss scoring low on this measure. Findings are discussed in terms of the disruptive effects of dysfunctional attitudes on assertive responding and their possible relationship to a cognitive vulnerability model of depression. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A rational analysis of the selection task as optimal data selection.

Human reasoning in hypothesis-testing tasks like P. C. Wason's (1968) selection task has been depicted as prone to systematic biases. However, performance on this task has been assessed against a now outmoded falsificationist philosophy of science. Therefore, the experimental data is reassessed in the light of a Bayesian model of optimal data selection in inductive hypothesis testing. The model provides a rational analysis (J. R. Anderson, 1990) of the selection task that fits well with people's performance on both abstract and thematic versions of the task. The model suggests that reasoning in these tasks may be rational rather than subject to systematic bias. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"The association between global and specific measures of the therapeutic relationship": Erratum.

Reports an error in "The association between global and specific measures of the therapeutic relationship" by Nick F. Coady and Elsa Marziali (Psychotherapy: Theory, Research, Practice, Training, 1994[Spr], Vol 31[1], 17-27). This article contained, as Figure 1, an SASB model. The authorship and copyrights for the model were not acknowledged. The following acknowledgement should have been included: "From Benjamin (1983), Intrex User's Manual. Intrex Interpersonal Institute, P.O. Box 581037, Salt Lake City, UT 84158. Reprinted by permission." An apology is offered to the author, Dr. Lorna Smith Benjamin. The particular version used in the article was developed in collaboration with Clinton W. McLemore. (The following abstract of the original article appeared in record 1994-46203-001.) Examined the association between global and specific measures of the therapeutic relationship in Sessions 3, 5, and 15 of 9 cases of time-limited psychodynamic psychotherapy. L. S. Benjamin's (see PA, Vol 53:2991; see also, 1984) structural analysis of social behavior (SASB) model provided the specific measure of relationship. There were more consistent associations between ratings of client contributions to the alliance and SASB ratings of client behaviors than there were for the same therapist variables. Additionally, analyses show that external (i.e., nonself) judgments of client and therapist contributions to the alliance, rather than therapist or client self-ratings of contributions to the alliance, were most frequently associated with the SASB behavior codes. Finally, different therapist and client behaviors seemed to be associated with quality of the therapeutic relationship at different points in the therapeutic process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Experimental designs, expectancy effects, and hypnotic analgesia.

40 undergraduates who scored high on the Harvard Group Scale of Hypnotic Susceptibility were randomly assigned to 1 of 4 groups. Each group received 3 60-sec immersions of cold-pressor pain stimulation. Immersions were associated with either hypnotic, waking, or no analgesia (control) instructions. The treatments and their order were varied across groups to induce different expectations about the efficacy of hypnotic and waking analgesia. Magnitude estimates and category scale ratings of pain indicated that hypnotic analgesia was more, less, or equally as effective as waking analgesia, depending on the expectations induced by varying treatment order. Pain ratings were also related to the type of cognitive activity (e.g., imaginative coping) engaged in during an immersion. (46 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)