Digital Conversion of Nonlinear Compensators with Antireset-Windup Compensation: Studies, Analysis and Design

All physically realizable systems are subject to saturations of one form or another. Control systems having saturations are susceptible to the nonlinear problem of reset-windup if the controllers within those systems contain one or more integrators. Reset-windup is a condition whereby the integrator continues to integrate the feedback error and add to the control signal, even in the presence of a decreasing error signal. This phenomenon can lead to excessive overshoot in the system in response to large setpoint changes. This paper discusses the problem of reset-windup in detail and presents several methods for correcting this problem in continuous-time systems as discussed in existing controls literature. Two approaches to the elimination of reset-windup are discussed in detail: the conventional anti-reset windup (CAW) scheme and the override signal (OS) scheme. The application of these methods to continuous-time systems is reviewed for simple example systems. The paper then proposes implementations of these methods for discrete-time systems, discusses problems associated with these implementations, including the phenomenon of chatter , and presents design criteria to make these implementations useful. Finally, the practical application of antireset-windup compensation is discussed through the design of a digital controller for an existing system

All auto shredding: evaluation of automotive shredder residue generated by shredding only vehicles.

A well developed infrastructure exists for the reuse and recycling of automotive parts and materials. At the end of a vehicle's useful life many parts are removed and sold for reuse and fluids are recovered for recycling or proper disposal. What remains is shredded, along with other metal bearing scrap such as home appliances, demolition debris and process equipment, and the metals are separated out and recycled. The remainder of the vehicle materials is call shredder residue which ends up in the landfill. As energy and natural resources becomes more treasured, increased effort has been afforded to find ways to reduce energy consumption and minimize the use of our limited resources. Many of the materials found in shredder residue could be recovered and help offset the use of energy and material consumption. For example, the energy content of the plastics and rubbers currently landfilled with the shredder residue is equivalent to 16 million barrels of oil per year. However, in the United States, the recovered materials, primarily polymers, cannot be recycled due to current regulatory barriers which preclude the re-introduction into commerce of certain materials because of residual contamination with substances of concern (SOCs) such as polychlorinated biphenyls (PCBs). The source of the PCBs is not well understood. Old transformers, capacitors, white goods and ballasts from lighting fixtures are likely contributing factors. The project was designed to evaluate whether vehicles of varying age and manufacturing origin contribute to the PCB content in shredder residue. Additionally, the project was designed to determine if there are any trends in material composition of the shredder residue from varied age and manufacturing groups. This information would aid in future material recovery facility strategy and design. The test utilized a newly installed shredder plant to shred four categories of automobiles. The categories were defined by vehicle age and the manufacturing company and location. Each category of vehicles was processed individually through the shredder plant and the resulting shredder residue was analyzed for its materials composition and presence of PCBs and leachable metals. The results show that shredder residue from all vehicle categories tested are not significant contributors of PCBs and leachable metals. It was evident that leachable cadmium levels have decreased in newer vehicles. The composition of the shredder residue from each of the four categories is similar to the others. In addition, these compositions are approximately equal to the composition of typical shredder residues, not limited to automotive materials

Becoming nature: effects of embodying a tree in immersive Virtual Reality on nature relatedness

The potential of using immersive virtual reality (iVR) technologies to enhance nature relatedness by embodying non-human beings, such as plants or animals, is only sparsely researched. To contribute to this emerging research field we conducted an experimental study (N = 28) that compared the effects of the viewing condition (iVR or desktop) while embodying a tree on nature relatedness, perspective-taking and, as a control, on perceived immersion. A mixed-method approach employing quantitative and qualitative questions was used. Our results showed that irrespective of condition allocation, the more immersed participants felt in their experience, the greater they reported increased levels of nature relatedness (r = 0.42, p < .05). While our quantitative data did yield a difference in immersion levels between the viewing condition (iVR vs. video, t(26) = 2.05, p = .05, d = .50) that did not translate into a stronger experimental effect of the iVR condition on nature relatedness (FInteraction(1,26) < 1). Regarding perspective taking, no significant differences between both groups emerged in the number of users who self-reported having fully taken on the perspective of the tree, (χ2(1) = 2.33, p = .127). However, only participants from the iVR group described their experience from a first-person perspective, suggesting a higher level of identification with the tree. This matches the observation that only those participants also reported self-reflective processes of their own role as a human being towards nature. Our results support previous research suggesting that experiencing nature via immersive VR in itself does not seem to suffice for creating an effect on nature relatedness. However, we observed that a higher perceived level of immersion for participants experiencing the embodiment of a tree in the iVR condition provoked reflective processes on one’s own role towards nature more strongly. We discuss the role of immersion and further factors to explain these differences and suggest steps for future research settings to help understand the beneficial potential of using immersive VR for nature relatedness.TU Berlin, Open-Access-Mittel - 202

Improving girls’ perception of computer science as a viable career option through game playing and design: Lessons from a systematic literature review

The objective of exposing girls to Computer Science as a career option has led to research directed towards gaming activities for girls. These activities include both game play and game design. Research about gaming activities for increasing girls’ interest in computer science has gained much attention over the past few years and has resulted in a number of contributions. We follow up with an overview of the status of research through a Systematic Literature Review. We investigate the relation between the various game playing or designing activities and their impact on girls’ perception of Computer Science as a career choice. We further present the design consideration for the games and related activities to potentially improve the perception of girls towards a Computer Science career. The applied method is a Systematic Literature Review through which we investigate which contributions were made, which knowledge areas were most explored, and which research facets have been used. We identify 25 papers to distill a common understanding of the state-of-the-art. Specifically, we investigate the effects that the game play/design activities had on girls’ perception about Computer Science; and what are the key design factors to be kept in mind while designing a serious game to improve girls’ perception about Computer Science. The results of this systematic literature review show that game playing or designing could indeed improve how girls perceive having a career in CS. The key aspects that such activities require are personalizing, opportunity for collaboration and the presence of a female lead characterThis work has been done during the tenure of an ERCIM Alain Bensoussan fellowshi

Microstructural mechanisms and advanced characterization of long and small fatigue crack growth in cast A356-T61 aluminum alloys

Fatigue crack growth-based design is a significant modern engineering consideration for the transportation sector, and its implementation requires accurate characterization and understanding of crack propagation mechanisms with respect to microstructure. To support this goal, long and small fatigue crack growth studies were conducted on widely used A356-T6 cast aluminum alloys in various microstructural conditions. Microstructural variations were created through processing and chemistry means in order to systematically investigate the individual and combined effects of the materials’ characteristic microstructural features on fatigue crack growth at all growth stages. Crack growth mechanisms and failure mode transitions are identified with respect to the eutectic Si morphology/distribution and grain structure by fractographic techniques and electron backscatter diffraction. Crack-microstructure interactions were investigated in depth across all crack sizes, and the respective roles of microstructural features were identified experimentally and further corroborated by numerical models. It is concluded that the eutectic Si phase enhances the alloys’ fatigue crack growth resistance in early growth stages (by transferring stresses off of the α-Al matrix), and progressively decreases due to damage localization. In later growth stages, the eutectic Si phase becomes increasingly detrimental to fatigue crack growth resistance because of its inherently low debonding strength and brittle fracture, as evidenced by the crack selectively following eutectic Si colonies

Somatic mosaicism and common genetic variation contribute to the risk of very-early-onset inflammatory bowel disease

Abstract: Very-early-onset inflammatory bowel disease (VEO-IBD) is a heterogeneous phenotype associated with a spectrum of rare Mendelian disorders. Here, we perform whole-exome-sequencing and genome-wide genotyping in 145 patients (median age-at-diagnosis of 3.5 years), in whom no Mendelian disorders were clinically suspected. In five patients we detect a primary immunodeficiency or enteropathy, with clinical consequences (XIAP, CYBA, SH2D1A, PCSK1). We also present a case study of a VEO-IBD patient with a mosaic de novo, pathogenic allele in CYBB. The mutation is present in ~70% of phagocytes and sufficient to result in defective bacterial handling but not life-threatening infections. Finally, we show that VEO-IBD patients have, on average, higher IBD polygenic risk scores than population controls (99 patients and 18,780 controls; P < 4 × 10−10), and replicate this finding in an independent cohort of VEO-IBD cases and controls (117 patients and 2,603 controls; P < 5 × 10−10). This discovery indicates that a polygenic component operates in VEO-IBD pathogenesis