Analysis and Insights from a Dynamical Model of Nuclear Plant Safety Risk

In this paper, we expand upon previously reported results of a dynamical systems model for the impact of plant processes and programmatic performance on nuclear plant safety risk. We utilize both analytical techniques and numerical simulations typical of the analysis of nonlinear dynamical systems to obtain insights important for effective risk management. This includes use of bifurcation diagrams to show that period doubling bifurcations and regions of chaotic dynamics can occur. We also investigate the impact of risk mitigating functions (equipment reliability and loss prevention) on plant safety risk and demonstrate that these functions are capable of improving risk to levels that are better than those that are represented in a traditional risk assessment. Next, we analyze the system response to the presence of external noise and obtain some conclusions with respect to the allocation of resources to ensure that safety is maintained at optimal levels. In particular, we demonstrate that the model supports the importance of management and regulator attention to plants that have demonstrated poor performance by providing an external stimulus to obtain desired improvements. Equally important, the model suggests that excessive intervention, by either plant management or regulatory authorities, can have a deleterious impact on safety for plants that are operating with very effective programs and processes. Finally, we propose a modification to the model that accounts for the impact of plant risk culture on process performance and plant safety risk. We then use numerical simulations to demonstrate the important safety benefits of a strong risk culture.Nonlinear Dynamical Systems, Process Model, Risk Management

A STUDY OF THE IMPACT OF SMALL-GROUP AND WHOLE-GROUP DISCUSSION ON THE CRITICAL THINKING DISPOSITIONS OF COMMUNITY COLLEGE ENGLISH COMPOSITION II STUDENTS

The area of critical thinking skills has been one of concern for many professionals working in the field of higher education (Nicholas & Raider-Roth, 2016; Shim & Walczak, 2012). The purpose of this study was to provide these professionals with sound pedagogical tools that can be used to assist college students in developing their critical thinking skills and dispositions. Using a sample of 34 English Composition II students from a community college in the Southeast, the researcher employed a pre-test/post-test comparison group design to compare the effects of small-group discussion of higher-order questions to the effects of whole-group discussion on students’ critical thinking dispositions. The students’ critical thinking dispositions were measured through the California Critical Thinking Disposition Inventory (CCTDI) (Facione, P., & Facione, N., 2007). Independent t-tests revealed no significant differences between the post-test composite and subscale CCTDI scores of students who addressed higher-order questions through small-group discussion and students who addressed the same questions via whole-group discussion. Despite the lack of significant findings, the study has implications for instructors wishing to use discussion as part of their critical thinking pedagogy

The Deceit of internet hate speech: A Study of the narrative and visual methods used by hate groups on the Internet

Intentional misinformation is a problem that has been documented in a variety of shapes and forms for thousands of years and continues to plague the American landscape. The advent and increasing usage of the Internet has created an additional venue through which intentional misinformation is disseminated, and many groups are taking full advantage of this new communication medium. Because the Internet allows anyone with web publishing skills to disseminate misinformation, it is often difficult for users to judge the credibility of the information. Hate groups understand this phenomenon and are taking full advantage of the Internet by publishing hate sites that promote their extremist ideologies by using language and symbolism that makes the true message difficult to decipher. This study will investigate the methods employed by hate groups to disseminate misinformation to the public

Dynamic properties in a family of competitive growing models

The properties of a wide variety of growing models, generically called $X/RD$, are studied by means of numerical simulations and analytic developments. The study comprises the following $X$ models: Ballistic Deposition, Random Deposition with Surface Relaxation, Das Sarma-Tamboronea, Kim-Kosterlitz, Lai-Das Sarma, Wolf-Villain, Large Curvature, and three additional models that are variants of the Ballistic Deposition model. It is shown that after a growing regime, the interface width becomes saturated at a crossover time ($t_{x2}$) that, by fixing the sample size, scales with $p$ according to $t_{x2}(p)\propto p^{-y}, \qquad (p > 0)$, where $y$ is an exponent. Also, the interface width at saturation ($W_{sat}$) scales as $W_{sat}(p)\propto p^{-\delta}, \qquad (p > 0)$, where $\delta$ is another exponent. It is proved that, in any dimension, the exponents $\delta$ and $y$ obey the following relationship: $\delta = y \beta_{RD}$, where $\beta_{RD} = 1/2$ is the growing exponent for $RD$. Furthermore, both exponents exhibit universality in the $p \to 0$ limit. By mapping the behaviour of the average height difference of two neighbouring sites in discrete models of type $X/RD$ and two kinds of random walks, we have determined the exact value of the exponent $\delta$. Finally, by linking four well-established universality classes (namely Edwards-Wilkinson, Kardar-Parisi-Zhang, Linear-MBE and Non-linear-MBE) with the properties of both random walks, eight different stochastic equations for all the competitive models studied are derived.Comment: 23 pages, 6 figures, Submitted to Phys. Rev.

Advanced radar absorbing ceramic-based materials for multifunctional applications in space environment

In this review, some results of the experimental activity carried out by the authors on advanced composite materials for space applications are reported. Composites are widely employed in the aerospace industry thanks to their lightweight and advanced thermo-mechanical and electrical properties. A critical issue to tackle using engineered materials for space activities is providing two or more specific functionalities by means of single items/components. In this scenario, carbon-based composites are believed to be ideal candidates for the forthcoming development of aerospace research and space missions, since a widespread variety of multi-functional structures are allowed by employing these materials. The research results described here suggest that hybrid ceramic/polymeric structures could be employed as spacecraft-specific subsystems in order to ensure extreme temperature withstanding and electromagnetic shielding behavior simultaneously. The morphological and thermo-mechanical analysis of carbon/carbon (C/C) three-dimensional (3D) shell prototypes is reported; then, the microwave characterization of multilayered carbon-filled micro-/nano-composite panels is described. Finally, the possibility of combining the C/C bulk with a carbon-reinforced skin in a synergic arrangement is discussed, with the aid of numerical and experimental analyses