Adaptive inverse control for helicopter vibration reduction

The reduction or alleviation of helicopter vibration will reduce maintenance requirements while at the same time increase ride quality and helicopter reliability. In forward flight, the helicopter's fuselage vibration spectrum tends to be dominated by multiples of the N/REV component. A way to use the method of adaptive inverse control to identify, in real-time, a controller capable of generating N/REV vibration of opposite phase to cancel the uncontrolled N/REV component is presented. Multicyclic feathering of blade pitch is the control considered

Bacharach and Burg Stahleck, 1817

Article describing and identifying as authentic a watercolour in the Hunterian collection which was recorded in the Turner literature but listed as location unknown

Review of Ashes in the Air by Ali Alizadeh

Review of Ashes in the Air by Ali Alizade

Closing the Certification Gaps in Adaptive Flight Control Software

Over the last five decades, extensive research has been performed to design and develop adaptive control systems for aerospace systems and other applications where the capability to change controller behavior at different operating conditions is highly desirable. Although adaptive flight control has been partially implemented through the use of gain-scheduled control, truly adaptive control systems using learning algorithms and on-line system identification methods have not seen commercial deployment. The reason is that the certification process for adaptive flight control software for use in national air space has not yet been decided. The purpose of this paper is to examine the gaps between the state-of-the-art methodologies used to certify conventional (i.e., non-adaptive) flight control system software and what will likely to be needed to satisfy FAA airworthiness requirements. These gaps include the lack of a certification plan or process guide, the need to develop verification and validation tools and methodologies to analyze adaptive controller stability and convergence, as well as the development of metrics to evaluate adaptive controller performance at off-nominal flight conditions. This paper presents the major certification gap areas, a description of the current state of the verification methodologies, and what further research efforts will likely be needed to close the gaps remaining in current certification practices. It is envisioned that closing the gap will require certain advances in simulation methods, comprehensive methods to determine learning algorithm stability and convergence rates, the development of performance metrics for adaptive controllers, the application of formal software assurance methods, the application of on-line software monitoring tools for adaptive controller health assessment, and the development of a certification case for adaptive system safety of flight

Certification of Safety-Critical Software Under DO-178C and DO-278A

The RTCA has recently released DO-178C and DO-278A as new certification guidance for the production of airborne and ground-based air traffic management software, respectively. Additionally, RTCA special committee SC-205 has also produced, at the same time, five other companion documents. These documents are RTCA DO-248C, DO-330, DO-331, DO- 332, and DO-333. These supplements address frequently asked questions about software certification, provide guidance on tool qualification requirements, and illustrate the modifications recommended to DO-178C when using model-based software design, object oriented programming, and formal methods. The objective of this paper is to first explain the relationship of DO-178C to the former DO-178B in order to give those familiar with DO- 178B an indication of what has been changed and what has not been changed. With this background, the relationship of DO-178C and DO-278 to the new DO-278A document for ground-based software development is shown. Last, an overview of the new guidance contained in the tool qualification document and the three new supplements to DO-178C and DO-278A is presented. For those unfamiliar with DO-178B, this paper serves to provide an entry point to this new certification guidance for airborne and ground-based CNS/ATM software certification

Mode of action and choice of antimalarial drugs for intermittent preventive treatment in infants.

Intermittent preventive treatment in infants (IPTi) is an effective and safe malaria control strategy. However, it remains unclear what antimalarials should be used to replace sulfadoxine-pyrimethamine (SP) when and where SP is no longer an effective drug for IPTi. Work recently conducted in Tanzania, combined with the findings of previous studies, indicates that IPTi is essentially intermittent chemoprophylaxis; consequently, long-acting antimalarials that provide a long period of post-treatment prophylaxis will be the most effective alternative to SP. However, because of concerns about development of drug resistance, new combinations of long-acting drugs are urgently needed

Criticality in a model of banking crises

An interbank market lets participants pool the risk arising from the combination of illiquid investments and random withdrawals by depositors. But it also creates the potential for one bank's failure to trigger off avalanches of further failures. We simulate a model of interbank lending to study the interplay of these two effects. We show that when banks are similar in size and exposure to risk, avalanche effects are small so that widening the interbank market leads to more stability. But as heterogeneity increases, avalanche effects become more important. By varying the heterogeneity and connectivity across banks, the system enters a critical regime with a power law distribution of avalanche sizes.Comment: presented at the conference Application of Physics in Economic Modelling, February 8 - 10, 2001, Pragu

Drop-In Clinics for Environmental Studies Students

The delivery of library instruction to students in those areas of the sciences and the social sciences dealing with biology and the environment has a long history (Bowden & Di Benedetto 2001; Kutner 2000; Kutner & Danks 2007; Sapp 2006; Sinn 1998). Often these instruction sessions take the form of a one hour lecture or workshop at the start of a semester before the students have begun their projects or papers. This "one-shot" approach, though popular, has its limitations. It may not be offered at a time when the students will actually start making use of library resources, it may not be tied very specifically to a particular assignment, or it may be too general in nature to be of much use to students later on when they need to look at particular topics in much more depth than can be addressed in one such session. The following article describes another approach: the strategic use of drop-in clinics as a method of instruction in which the students themselves determine how the instruction proceeds