Safe and optimal navigation for autonomous multi-rotor aerial vehicle in a dynamic known environment by a decomposition-coordination method

In this paper, we present a new solution for the Autonomous navigation problem, using a Decomposition-Coordination Method (DCM) 1. The main purpose of this work is to compute an optimal and safe path for the multi-rotor Unmanned Aerial Vehicle (UAV) in a dynamic environment, moving from an initial location to the desired state. We assume that the flight environment is totally known to a supervisory unit, and the positions and trajectories of dynamic obstacles could be known in real-time, thus to perform in such environment a high reactivity is required as well as good connectivity with the supervisory unit that provides the safe path, each time one obstacle or more are detected on the road, so that the UAV could autonomously diverts from the unsafe path to the new safe one, and avoid the potential collisions. First and foremost, we choose a generalized nonlinear model for the multi-rotors in view of the rotational and translational dynamics of the UAV. We then associate that model with the objective functions. After that, we proceed to the resolution of the multi-objective optimization problem using our approach of decomposition-coordination. The principle of this method consists in decomposing the system into several smaller subsystems to simplify the treatment. Then we achieve the coordination afterward using Lagrange multipliers. To prove the convergence and stability of our method we make use of a Lyapunov function chosen particularly for this system. In the last section we present the simulation results, to confirm the reliability of our method.     

When History Seems to Repeat Itself: Exposure to Perceived Lessons of the Past Influences Predictions About Current Political Events

The idea that the past holds lessons for the present, under the guise of historical analogies, is prevalent in political and public discourse. Those analogies are often accompanied by dire warnings befalling those who “forget” or otherwise neglect the powerful lessons of History—and would then be “doomed to repeat it”, as the saying goes. So, Would remembering history make it seem more OR LESS likely to repeat itself in the future? In other words, does exposure to specific lessons about past events, especially ones involving causal claims, affect how people expect real-life events to turn out? Four studies (three preregistered) tested this experimentally. In Studies 1 and 2, participants expected the same behavior (the US adopting a harsh stance against Iran in the Nuclear Treaty) to result in a more negative outcome when this current stance seemed to match a “lesson” they had read about the break-out of World War II (European leaders adopting a harsh approach against Germany in the 1919 Versailles Treaty vs. a conciliatory approach in the 1938 Munich Agreement). Studies 3 and 4 attempted to eliminate some confounds present in the first two studies and to generalize the effect to different events. While results varied across studies, an internal meta-analysis indicated that the analogical effect on predictions (d = –.08) tended to become stronger as participants’ knowledge about the target situation decreased (d-1SD = –.24). These findings support the possibility of analogical-based predictive effects for real-life political events, and are discussed in light of their research and political implications.     

Acali,Ra 1, and Ra 2: Some conclusions and hypotheses concerning human friction under isolation and stress,with special reference to intelligence and personaiity assessment

Eleven adult volunteers - six females and five males - were left on a small raft in the Atlantic in order to study interpersonal relationships affected by family patterns of behavior, attitudes toward sex, race and racism, nationality, verbal and nonverbal communication, personality and character, intelligence, language, religion, leadership roles, and space. We hoped to gain a better understanding of friction and violence phenomena. The Acali experiment grew out of the more limited raft studies of Ra 1 and Ra 2. Intelligence and personality of the 11 members of the Acali raft expedition of 1973 were assessed by crew members and by shore-based scientists. Predictions concerning the Likely outcome of this long period of unavoidable proximity to 10 other individuals were made by a variety of scientists. Media treatment and views of friends and relatives were also studied. Some of the basic findings of the study were that assessments of both intelligence and personality carried out by these two methods were very different. Practising artists showed better predictive powers concerning the outcome of the voyage than either natural or social scientists. Media treatment influenced the views of the relatives of volunteers. It is suggested that laboratory assessments may not be related to assessed performances under stress, and that further progress in understanding human hostility will depend on a better knowledge of individual interactions.     

Empirically Defining Treatment Response and Remission in Body Dysmorphic Disorder Using a Short Self-Report Instrument

Determining response or remission status in body dysmorphic disorder (BDD) usually requires a lengthy interview with a trained clinician. This study sought to establish empirically derived cutoffs to define treatment response and remission in BDD using a brief self-report instrument, the Appearance Anxiety Inventory (AAI). Results from three clinical trials of BDD were pooled to create a sample of 123 individuals who had received cognitive-behavioral therapy for BDD, delivered via the Internet. The AAI was compared to gold-standard criteria for response and remission in BDD, based on the clinician-administered Yale–Brown Obsessive Compulsive Scale, modified for BDD (BDD-YBOCS), and evaluated using signal detection analysis. The results showed that a ≥ 40% reduction on the AAI best corresponded to treatment response, with a sensitivity of 0.71 and a specificity of 0.84. A score ≤ 13 at posttreatment was the optimal cutoff in determining full or partial remission from BDD, with a sensitivity of 0.75 and a specificity of 0.88. These findings provide benchmarks for using the AAI in BDD treatment evaluation when resource-intensive measures administered by clinicians are not feasible.     

Exploring the “clutch” in clutch performance: A qualitative investigation of the experience of pressure in successful performance

ObjectivesThe term “clutch” is colloquially used to describe important or crucial situations in sport, with clutch performance referring to successful performances during these pressurised circumstances. Positioning the clutch as an objective, situational variable, however, may not account for the athletes' subjective appraisal of such situations. Accordingly, this study aimed to explore athletes' perceptions of clutch situations, and further, how these perceptions influenced their performance.MethodSixteen athletes (M_age = 26.88 years) participated in event-focused, semi-structured interviews soon after a clutch performance (M = 4 days later). Data were analysed utilising reflexive thematic analysis.ResultsFour themes were generated: (1) the clutch involves situational and subjective factors, suggesting that the appraisal of the clutch is influenced by situational and subjective components; (2) the perception of the clutch comes and goes, suggesting that there may be multiple, fluctuating episodes of the clutch within an event; (3) pressure affects performance, and performance affects pressure, suggesting that the appraisal of pressure was perceived to impact performance, and that performance also influenced appraisal of pressure; and, (4) experience of anxiety during the clutch is varied, suggesting that the experience of anxiety is not inherent to clutch performance.ConclusionsThe clutch has traditionally been considered an objective, situational variable. This study suggests, however, that the clutch relies upon the athlete appraising pressure in response to these situational variables, which may not always occur. Further, other subjective factors may increase the appraisal of pressure, suggesting that the clutch cannot solely be considered as a situational variable.     

Perceived coach-autonomy support, basic need satisfaction and the well- and ill-being of elite youth soccer players: A longitudinal investigation

Objectives

Drawing from the basic needs theory [BNT; Ryan, R. M., & Deci, E. L. (2002). An overview of self-determination theory. In E. L. Deci, & R. M. Ryan (Eds.), Handbook of self-determination research (pp. 3-33). Rochester, NY: University of Rochester Press], the major purpose of the present study was to test a hypothesized sequence of temporal relationships between perceptions of coach-autonomy support, basic need satisfaction and indices of well- and ill-being. A subsidiary aim was to ascertain the assumed mediational role of basic need satisfaction in explicating the perceived autonomy support and well-/ill-being relationships over time.

Design

A field-based longitudinal design was employed.

Methods

Participants (N = 54 males) from an elite youth soccer academy in the UK completed a multi-section questionnaire tapping the targeted variables on six occasions across two competitive seasons.

Results

Multi-level regression analyses revealed that perceptions of coach-autonomy support positively predicted within-person changes and between-person mean differences in basic need satisfaction and well-being over time. Satisfaction scores for the needs for competence and relatedness were found to predict within-person changes in subjective vitality. These same needs partially mediated the coach-autonomy support-subjective vitality link over the two seasons.

Conclusions

The findings partially support the tenets of BNT, and are discussed in terms of their practical application to participants involved in an elite youth sport setting.     

The postural control can be optimized by the first movement initiation condition encountered when submitted to muscle fatigue

We investigated whether and how the movement initiation condition (IC) encountered during the early movements performed following focal muscle fatigue affects the postural control of discrete ballistic movements. For this purpose, subjects performed shoulder flexions in a standing posture at maximal velocity under two movement IC, i.e., in self-paced conditions and submitted to a Stroop-like task in which participants had to trigger fast shoulder flexions at the presentation of incongruent colors. Shoulder flexion kinematics, surface muscle activity of focal and postural muscles as well as center-of-pressure kinematics were recorded. The initial IC and the order in which subjects were submitted to these two conditions were varied within two separate experimental sessions. IC schedule was repeated before and after fatigue protocols involving shoulder flexors. The aim of this fatigue procedure was to affect acceleration-generating capacities of focal muscles. In such conditions, the postural muscle activity preceding and accompanying movement execution is expected to decrease. Following fatigue, when subjects initially moved in self-paced conditions, postural muscle activity decreased and scaled to the lower focal peak acceleration. This postural strategy then transferred to the Stroop-like task. In contrast, when subjects initially moved submitted to the Stroop-like task, postural muscle activity did not decrease and this transferred to self-paced movements. Regarding the center-of-pressure peak velocity, which is indicative of the efficiency of the postural actions generated in stabilizing posture, no difference appeared between the two sessions post-fatigue. This highlights an optimization of the postural actions when subjects first moved in self-paced conditions, smaller postural muscle activation levels resulting in similar postural consequences. In conclusion, the level of neuromuscular activity associated with the postural control is affected and can be optimized by the initial movement IC experienced post-fatigue. Beyond the fundamental contributions arising from these results, we point out potential applications for trainers and sports instructors.     

Optimal matching analysis in career research: A review and some best-practice recommendations

Optimal matching is a method for the analysis of sequential data. It allows researchers to detect patterns in career sequences or occupational trajectories. We first give a brief introduction to the method and review the existing career literature that employs optimal matching. To examine which data properties are required for optimal matching analysis, we conducted Monte Carlo simulations of career sequences with varying parameters for sequence length, sample size and missing items. We find that sequence length is the relevant factor for correct results, while sample size does not substantially affect result quality. Another important finding is that sequences with up to 30% elements missing can be used for optimal matching analysis. We also show which settings for the optimal matching procedure deliver the best results.     

Subliminal action priming modulates the perceived intensity of sensory action consequences

The sense of control over the consequences of one’s actions depends on predictions about these consequences. According to an influential computational model, consistency between predicted and observed action consequences attenuates perceived stimulus intensity, which might provide a marker of agentic control. An important assumption of this model is that these predictions are generated within the motor system. However, previous studies of sensory attenuation have typically confounded motor-specific perceptual modulation with perceptual effects of stimulus predictability that are not specific to motor action. As a result, these studies cannot unambiguously attribute sensory attenuation to a motor locus. We present a psychophysical experiment on auditory attenuation that avoids this pitfall. Subliminal masked priming of motor actions with compatible prime–target pairs has previously been shown to modulate both reaction times and the explicit feeling of control over action consequences. Here, we demonstrate reduced perceived loudness of tones caused by compatibly primed actions. Importantly, this modulation results from a manipulation of motor processing and is not confounded by stimulus predictability. We discuss our results with respect to theoretical models of the mechanisms underlying sensory attenuation and subliminal motor priming.     

Optimal correction for guessing in multiple-choice tests

Subjects’ decisions in multiple-choice tests are an interesting domain for the analysis of decision making under uncertainty. When the test is graded using a rule that penalizes wrong answers, each item can be viewed as a lottery where a rational examinee would choose whether to omit (sure reward) or answer (take the lottery) depending on risk aversion and level of knowledge. We formalize students as heterogeneous decision makers with different risk attitudes and levels of knowledge. Building on IRT, we compute the optimal penalty given students’ optimal behavior and the trade-off between bias and measurement error. Although MCQ examinations are frequently used, there is no consensus as to whether a penalty for wrong answers should be used or not. For example, examinations for medical licensing in some countries include MCQ sections with penalty while in others there is no penalty for wrong answers. We contribute to this discussion with a formal analysis of the effects of penalties; our simulations indicate that the optimal penalty is relatively high for perfectly rational students but also when they are not fully rational: even though penalty discriminates against risk averse students, this effect is small compared with the measurement error that it prevents.