Book Review. - Literatur

Book Review. - Literatu

Multiple Model Adaptive Estimation and Control Redistribution for the Vista F-16

Performance characteristics of a Multiple Model Adaptive Estimation and Control Redistribution (MMAE/CR) algorithm are evaluated against single and double actuator and sensor failures. MMAE alone can compensate for sensor failures, whereas Control Redistribution compensates for actuator failures by redistributing commands, initially intended for failed actuators, to the unfailed actuators in such a way that the desired system response is achieved. Both failure detection and compensation capabilities are developed and analyzed through an extensive amount of simulation data, particularly addressing multiple failures. Simulations are performed utilizing the high fidelity, non-linear six degree of freedom Simulation Rapid Prototyping Facility for the VISTA F-16, for both benign and maneuvering scenarios. Methods utilized to incorporate the MMAE/CR techniques are examined and modifications required to enhance performance are also presented. Results are presented which indicate the techniques incorporated provide an excellent means of both failure detection and compensation for the failures of both actuators and sensors. Approximately 98 percent of all secondary failures were successfully detected, and the majority of these detections are shown to occur in less than .5 seconds. The techniques of Multiple Model Adaptive Estimation and Control Redistribution are shown to complement each other well by providing improved failure detection in the face of actuator failures through the redistribution of the dither signal (used to enhance identifiability when there are no maneuvering commands to excite the system), and improved control authority through enhanced state variable estimation in the face of sensor failures

Book Review. - Literatur

Book Review. - Literatu

Perceptions of Race, Status, and Instructional Modality as Predictors of Degree Attainment for African American Male Community College Students

Given the large number of students who begin their college education yet never graduate, it is essential that, as higher education leaders and policymakers develop student success strategies, they consider the persistence and degree attainment dynamics of all populations. This study focuses on the problem of degree attainment from the perspective of male, second-year, African American, community college students. A qualitative narrative case study approach was used to ascertain their perception of race, status attainment, and instructional learning modalities as predictors of degree attainment. Accordingly, those perceptions were then evaluated to determine their utility as predictors of degree attainment. Six students were recruited via electronically distributed flyers and participated in semistructured interviews via Zoom. The research questions focused on these students’ perceptions of learning modalities and additional supports offered at their community college, how status attainment impacted their academic persistence, and what these male, second-year, African American, community college students perceived as institutional barriers to degree attainment. The data were hand-coded and revealed 11 emergent themes. The emergent themes were further analyzed using NVivo, revealing three primary themes categorized as follows: (a) Representation, (b) Support and (c) Race. The findings revealed that in as much as the research participants embraced the challenges within their learning environment, they perceived the need for additional support services, which they felt would contribute to retention and eventual degree attainment. Moreover, the findings also revealed that while the student generally did not experience overt racism, they still perceived institutional barriers to degree attainment grounded in implicitly biased interactions on campus. Accordingly, the perceived biases influenced these students’ perception of status as it relates to a student’s perception of self and how others view him, and also a perception of self within the context of economic and social status. Hence, this study discusses these findings and provides new insights into predictors of academic persistence and degree attainment of African American, male, community college students

Neural superposition and oscillations in the eye of the blowfly

Neural superposition in the eye of the blowfly Calliphora erythrocephala was investigated by stimulating single photoreceptors using corneal neutralization through water immersion. Responses in Large Monopolar Cells (LMCs) in the lamina were measured, while stimulating one or more of the six photoreceptors connected to the LMC. Responses to flashes of low light intensity on individual photoreceptors add approximately linearly at the LMC. Higher intensity light flashes produce a maximum LMC response to illumination of single photoreceptors which is about half the maximum response to simultaneous illumination of the six connecting photoreceptors. This observation indicates that a saturation can occur at a stage of synaptic transmission which precedes the change in the post-synaptic membrane potential. Stimulation of single photoreceptors yields high frequency oscillations (about 200 Hz) in the LMC potential, much larger in amplitude than produced by simultaneous stimulation of the six photoreceptors connected to the LMC. It is discussed that these oscillations also arise from a mechanism that precedes the change in the postsynaptic membrane potential.

Towards a Standard Approach for Wear Testing of Wheel and Rail Materials

Examination of the literature for wear testing methodologies for wheel and rail material reveals that while only a few different techniques have been used there is a wide variety in exactly how the tests have been conducted and the resulting data reported. This makes comparison of the data very difficult. This work, carried out as part of the International Collaborative Research Initiative (ICRI) which is aiming to bring together wheel/rail interface researchers from across the world to collate data and knowledge to try to solve some of the common problems that are faced, has examined the different approaches used and attempted to pull together all the good practice used into a test specification for future twin disc testing for wheel and rail materials. Adoption of the method will allow data to be compared reliably and eventually enable data to be compiled into wear maps to use as input, for example, to multi-body dynamics simulation wear prediction tools

In vitro 3D tissue modelling: Insights into ameloblastoma pathogenesis

Ameloblastoma is a rare, benign oral tumour. Tumours develop within the jaw bone and are highly destructive and invasive, with cells migrating into the jaw and surrounding soft tissue. This is a little-understood disease which if left untreated causes dramatic bone destruction and maxillofacial disfigurement. Current treatment is radical surgery, often resulting in extensive loss of function and tissue. An ameloblastoma-derived cell line, AM-1, has been established [1]. Cells were isolated from a human tumour and immortalised by the addition of HPV-16 DNA. This study aims to (i) make a 3D in vitro ameloblastoma disease model, using plastic-compressed collagen gel [2] seeded with AM-1 cells, and (ii) use this bone construct to characterise tissue remodelling, cell growth and invasiveness

NEXP-completeness and Universal Hardness Results for Justification Logic

We provide a lower complexity bound for the satisfiability problem of a multi-agent justification logic, establishing that the general NEXP upper bound from our previous work is tight. We then use a simple modification of the corresponding reduction to prove that satisfiability for all multi-agent justification logics from there is hard for the Sigma 2 p class of the second level of the polynomial hierarchy - given certain reasonable conditions. Our methods improve on these required conditions for the same lower bound for the single-agent justification logics, proven by Buss and Kuznets in 2009, thus answering one of their open questions.Comment: Shorter version has been accepted for publication by CSR 201

Challenges in Chagas Disease Drug Development.

The protozoan parasite Trypanosoma cruzi causes Chagas disease, an important public health problem throughout Latin America. Current therapeutic options are characterised by limited efficacy, long treatment regimens and frequent toxic side-effects. Advances in this area have been compromised by gaps in our knowledge of disease pathogenesis, parasite biology and drug activity. Nevertheless, several factors have come together to create a more optimistic scenario. Drug-based research has become more systematic, with increased collaborations between the academic and commercial sectors, often within the framework of not-for-profit consortia. High-throughput screening of compound libraries is being widely applied, and new technical advances are helping to streamline the drug development pipeline. In addition, drug repurposing and optimisation of current treatment regimens, informed by laboratory research, are providing a basis for new clinical trials. Here, we will provide an overview of the current status of Chagas disease drug development, highlight those areas where progress can be expected, and describe how fundamental research is helping to underpin the process

Recent Basal Melting of a Mid-Latitude Glacier on Mars

Evidence for past basal melting of young (late Amazonian), debris-covered glaciers in Mars’ mid-latitudes is extremely rare. Thus, it is widely thought that these viscous flow features (VFFs) have been perennially frozen to their beds. We identify an instance of recent, localized wet-based mid-latitude glaciation, evidenced by a candidate esker emerging from a VFF in a tectonic rift in Tempe Terra. Eskers are sedimentary ridges deposited in ice-walled meltwater conduits and are indicative of glacial melting. We compare the candidate esker to terrestrial analogues, present a geomorphic map of landforms in the rift, and develop a landsystem model to explain their formation. We propose that the candidate esker formed during a transient phase of wet-based glaciation. We then consider the similarity between the geologic setting of the new candidate esker and that of the only other candidate esker to be identified in association with an existing mid-latitude VFF; both are within tectonic graben/rifts proximal to volcanic provinces. Finally, we calculate potential basal temperatures for a range of VFF thicknesses, driving stresses, mean annual surface temperatures, and geothermal heat fluxes, which unlike previous studies, include the possible role of internal strain heating. Strain heating can form an important additional heat source, especially in flow convergence zones, or where ice is warmer due to elevated surface temperatures or geothermal heat flux. Elevated geothermal heat flux within rifts, perhaps combined with locally-elevated strain heating, may have permitted wet-based glaciation during the late Amazonian, when cold climates precluded more extensive wet-based glaciation on Mars