Joint preload properties of structural threaded fasteners

Proper installation techniques are described and reliable torque-tension values are presented on joint preload /or clamp load/ properties of structural threaded fasteners

Suspended Load Path Tracking Control Using a Tilt-rotor UAV Based on Zonotopic State Estimation

This work addresses the problem of path tracking control of a suspended load using a tilt-rotor UAV. The main challenge in controlling this kind of system arises from the dynamic behavior imposed by the load, which is usually coupled to the UAV by means of a rope, adding unactuated degrees of freedom to the whole system. Furthermore, to perform the load transportation it is often needed the knowledge of the load position to accomplish the task. Since available sensors are commonly embedded in the mobile platform, information on the load position may not be directly available. To solve this problem in this work, initially, the kinematics of the multi-body mechanical system are formulated from the load's perspective, from which a detailed dynamic model is derived using the Euler-Lagrange approach, yielding a highly coupled, nonlinear state-space representation of the system, affine in the inputs, with the load's position and orientation directly represented by state variables. A zonotopic state estimator is proposed to solve the problem of estimating the load position and orientation, which is formulated based on sensors located at the aircraft, with different sampling times, and unknown-but-bounded measurement noise. To solve the path tracking problem, a discrete-time mixed $\mathcal{H}_2/\mathcal{H}_\infty$ controller with pole-placement constraints is designed with guaranteed time-response properties and robust to unmodeled dynamics, parametric uncertainties, and external disturbances. Results from numerical experiments, performed in a platform based on the Gazebo simulator and on a Computer Aided Design (CAD) model of the system, are presented to corroborate the performance of the zonotopic state estimator along with the designed controller

Spatial stochasticity and non-continuum effects in gas flows

We investigate the relationship between spatial stochasticity and non-continuum effects in gas flows. A kinetic model for a dilute gas is developed using strictly a stochastic molecular model reasoning, without primarily referring to either the Liouville or the Boltzmann equations for dilute gases. The kinetic equation, a stochastic version of the well-known deterministic Boltzmann equation for dilute gas, is then associated with a set of macroscopic equations for the case of a monatomic gas. Tests based on a heat conduction configuration and sound wave dispersion show that spatial stochasticity can explain some non-continuum effects seen in gases

Self Trapping of a Single Bacterium in its Own Chemoattractant

Bacteria (e.g. E. Coli) are very sensitive to certain chemoattractants (e.g. asparate) which they themselves produce. This leads to chemical instabilities in a uniform population. We discuss here the different case of a single bacterium, following the general scheme of Brenner, Levitov and Budrene. We show that in one and two dimensions (in a capillary or in a thin film) the bacterium can become self-trapped in its cloud of attractant. This should occur if a certain coupling constant $g$ is larger than unity. We then estimate the reduced diffusion D_eff of the bacterium in the strong coupling limit, and find D_eff ~ 1/g.Comment: 4 pages, absolutely no figure

Neuronal and non-neuronal signals regulate <i>Caernorhabditis elegans</i> avoidance of contaminated food

One way in which animals minimise the risk of infection is to reduce their contact with contaminated food. Here we establish a model of pathogen-contaminated food avoidance using the nematode worm Caernorhabditis elegans. We find that avoidance of pathogen-contaminated food protects C. elegans from the deleterious effects of infection and, using genetic approaches, demonstrate that multiple sensory neurons are required for this avoidance behaviour. In addition, our results reveal that avoidance of contaminated food requires bacterial adherence to non-neuronal cells in the tail of C. elegans that are also required for the cellular immune response. Previous studies in C. elegans have contributed significantly to our understanding of molecular and cellular basis of host-pathogen interactions and our model provides a unique opportunity to gain basic insights into how animals avoid contaminated food

Imagining a New Nation: Patriotism and National Identity in the Writing of Late-18th Century American Women

Benedict Anderson defined the nation as “an imagined political community” that is “imagined as both inherently limited and sovereign.” The research for this paper began with a desire to know how American women in the time leading up to, during, and immediately after the American Revolution and War of Independence did or did not imagine themselves as members of the newly emerging political community eventually known as the United States of America. As tensions between the Colonies and Great Britain increased, as tea was dumped in Boston harbor, and as independence was declared in 1776, how did women make sense of these events and their significance for their own identities? As many colonists began to reject their previous identity as British subjects and colonial residents in favor of a new civic identity as members of a separate, sovereign nation, they needed to define what it meant to be American. Who was an American citizen? What did it mean to be an American citizen? What was it that bound the disparate thirteen colonies and their diverse populations together into one cohesive nation? Where were the limits to this newly imagined community, and did these limits include or exclude women

Epistemic Harm in Empathy

This paper delves into the intricacies of the concept of epistemic harm. Particularly, epistemic harm is used as a case study to gain insights into the efficacy and distinctiveness of the concept of harm vis-à-vis related constructs such as violence and trauma within the domain of social psychology. The paper underscores the pertinence of the concept of epistemic harm in the context of empathetic testimonial exchange using autism studies as a sample case. Subsequently, empathy is characterised as innately engendering epistemic harm, manifesting both at the inter-subjective and intra-subjective levels. The paper concludes with a contemplation on the significance of the idea of epistemic harm within the broader field of harm research

Identity as a Determinant of the Overreporting of Church Attendance in Canada

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91358/1/j.1468-5906.2012.01640.x.pd