Tracking control of nonlinear automobile idle-speed time-delay system via differential geometry approach

This paper is concerned with the problem of global asymptotical tracking of single-input single-output (SISO) nonlinear time-delay control systems. Based on the input-output feedback linearization technique and Lyapunov method for nonlinear state feedback synthesis, a robust globally asymptotical output tracking controller design methodology for a broad class of nonlinear time-delay control systems is developed. The underlying theoretical approaches are the differential geometry approach and the composite Lyapunov approach. One utilizes the parameterized co-ordinate transformation to transform the original nonlinear system into singularly perturbed model and the composite Lyapunov approach is then applied for output tracking. For the view of practical application, the proposed control methodology has been successfully applied to the famous nonlinear automobile idle-speed control system.     

Space,relations, and the learning of science

In the literature on the situated and distributed nature of cognition, the coordination of spatial organization and the structure of human practices and relations is accepted as a fact. To date, science educators have yet to build on such research. Drawing on an ethnographic study of high school students during an internship in a scientific research laboratory, which we understand as a “perspicuous setting” and a “smart setting,” in which otherwise invisible dimensions of human practices become evident, we analyze the relationship between spatial configurations of the setting and the nature and temporal organization of knowing and learning in science. Our analyses show that spatial aspects of the laboratory projectively organize how participants act and can serve as resources to help the novices to participate in difficult and unfamiliar tasks. First, existing spatial relations projectively organize the language involving interns and lab members. In particular, spatial relations projectively organize where and when pedagogical language should happen; and there are specific discursive mechanisms that produce cohesion in language across different places in the laboratory. Second, the spatial arrangements projectively organize the temporal dimensions of action. These findings allow science educators to think explicitly about organizing “smart contexts” that help learners participate in and learn complex scientific laboratory practices.     

Placement disruption and negative placement outcomes among adolescents in long-term foster care: the role of behavior problems

OBJECTIVE: This study examined risk of placement disruption and negative placement outcomes (e.g., residential treatment and incarceration) among adolescents placed in traditional family foster care for a year or longer. A foster parent's report of externalizing behavior problems was expected to be a stronger predictor of disruption and negative outcomes than a caseworker's report. Additionally, the association between behavior problems and placement disruption was expected to be mediated by the youth's degree of belonging and integration in the foster home. METHOD: The caseworkers and foster parents of 179 randomly selected 12-13-year-old adolescents placed in traditional foster care were interviewed by telephone. Interviews included standardized measures of externalizing behavioral problems and several other variables that have been previously associated with placement movement. Disruption from the youth's foster home at the time of the interview was prospectively tracked for 5 years. RESULTS: Over half of the youth experienced a disruption of their placement. Contrary to expectations, behavior problems as reported by caseworkers, but not foster parents, were predictive of placement disruption. However, the foster parent's report of behavior problems predicted risk of negative outcome after a period of 5 years. As hypothesized, integration in the foster home was highly predictive of placement stability and mediated the association between behavior problems and risk of disruption. CONCLUSIONS: Results suggest that integration in the foster home might be an important dimension of placement adaptation that should be considered during service planning for foster youth in long-term foster care. In addition, using standardized measures of behavior with both foster parents and caseworkers might be necessary to assess both long-term risk of negative outcomes and more immediate risk of placement disruption.     

Diagnosing Global Case Influence on MAR Versus MNAR Model Comparisons

When missingness is suspected to be not at random (MNAR) in longitudinal studies, researchers sometimes compare the fit of a target model that assumes missingness at random (here termed a MAR model) and a model that accommodates a hypothesized MNAR missingness mechanism (here termed a MNAR model). It is well known that such comparisons are only interpretable conditional on the validity of the chosen MNAR model’s assumptions about the missingness mechanism. For that reason, researchers often perform a sensitivity analysis comparing the MAR model to not one, but several, plausible alternative MNAR models. In the social sciences, it is not widely known that such model comparisons can be particularly sensitive to case influence, such that conclusions drawn could depend on a single case. This article describes two convenient diagnostics suited for detecting case influence on MAR–MNAR model comparisons. Both diagnostics require much less computational burden than global influence diagnostics that have been used in other disciplines for MNAR sensitivity analyses. We illustrate the interpretation and implementation of these diagnostics with simulated and empirical latent growth modeling examples. It is hoped that this article increases awareness of the potential for case influence on MAR–MNAR model comparisons and how it could be detected in longitudinal social science applications.     

Fitting Nonlinear Latent Growth Curve Models With Individually Varying Time Points

Individual growth trajectories of psychological phenomena are often theorized to be nonlinear. Additionally, individuals’ measurement schedules might be unique. In a structural equation framework, latent growth curve model (LGM) applications typically have either (a) modeled nonlinearity assuming some degree of balance in measurement schedules, or (b) accommodated truly individually varying time points, assuming linear growth. This article describes how to fit 4 popular nonlinear LGMs (polynomial, shape-factor, piecewise, and structured latent curve) with truly individually varying time points, via a definition variable approach. The extension is straightforward for certain nonlinear LGMs (e.g., polynomial and structured latent curve) but in the case of shape-factor LGMs requires a reexpression of the model, and in the case of piecewise LGMs requires introduction of a general framework for imparting piecewise structure, along with tools for its automation. All 4 nonlinear LGMs with individually varying time scores are demonstrated using an empirical example on infant weight, and software syntax is provided. The discussion highlights some advantages of modeling nonlinear growth within structural equation versus multilevel frameworks, when time scores individually vary.     

Effects of 3D Printing Project-based Learning on Preservice Elementary Teachers’ Science Attitudes,Science Content Knowledge,and Anxiety About Teaching Science

3D printing technology is a powerful educational tool that can promote integrative STEM education by connecting engineering, technology, and applications of science concepts. Yet, research on the integration of 3D printing technology in formal educational contexts is extremely limited. This study engaged preservice elementary teachers (N?=?42) in a 3D Printing Science Project that modeled a science experiment in the elementary classroom on why things float or sink using 3D printed boats. The goal was to explore how collaborative 3D printing inquiry-based learning experiences affected preservice teachers’ science teaching self-efficacy beliefs, anxiety toward teaching science, interest in science, perceived competence in K-3 technology and engineering science standards, and science content knowledge. The 3D printing project intervention significantly decreased participants’ science teaching anxiety and improved their science teaching efficacy, science interest, and perceived competence in K-3 technological and engineering design science standards. Moreover, an analysis of students’ project reflections and boat designs provided an insight into their collaborative 3D modeling design experiences. The study makes a contribution to the scarce body of knowledge on how teacher preparation programs can utilize 3D printing technology as a means of preparing prospective teachers to implement the recently adopted engineering and technology standards in K-12 science education.     

Eye movement patterns of captioned television viewers

Eye movement of six subjects was recorded as they watched video segments with and without captions. It was found that the addition of captions to a video resulted in major changes in eye movement patterns, with the viewing process becoming primarily a reading process. Further, although people viewing a specific video segment are likely to have similar eye movement patterns, there are also distinct individual differences present in these patterns. For example, someone accustomed to speechreading may spend more time looking at an actor's lips, while someone with poor English skills may spend more time reading the captions. Finally, there is some preliminary evidence to suggest that higher captioning speed results in more time spent reading captions on a video segment.