Decentralized Formation Flying Control in a Multiple-Team Hierarchy

This paper presents the prototype of a system that addresses these objectives-a decentralized guidance and control system that is distributed across spacecraft using a multiple-team framework. The objective is to divide large clusters into teams of manageable size, so that the communication and computational demands driven by N decentralized units are related to the number of satellites in a team rather than the entire cluster. The system is designed to provide a high-level of autonomy, to support clusters with large numbers of satellites, to enable the number of spacecraft in the cluster to change post-launch, and to provide for on-orbit software modification. The distributed guidance and control system will be implemented in an object-oriented style using MANTA (Messaging Architecture for Networking and Threaded Applications). In this architecture, tasks may be remotely added, removed or replaced post-launch to increase mission flexibility and robustness. This built-in adaptability will allow software modifications to be made on-orbit in a robust manner. The prototype system, which is implemented in MATLAB, emulates the object-oriented and message-passing features of the MANTA software. In this paper, the multiple-team organization of the cluster is described, and the modular software architecture is presented. The relative dynamics in eccentric reference orbits is reviewed, and families of periodic, relative trajectories are identified, expressed as sets of static geometric parameters. The guidance law design is presented, and an example reconfiguration scenario is used to illustrate the distributed process of assigning geometric goals to the cluster. Next, a decentralized maneuver planning approach is presented that utilizes linear-programming methods to enact reconfiguration and coarse formation keeping maneuvers. Finally, a method for performing online collision avoidance is discussed, and an example is provided to gauge its performance

Certification Considerations for Adaptive Systems

Advanced capabilities planned for the next generation of aircraft, including those that will operate within the Next Generation Air Transportation System (NextGen), will necessarily include complex new algorithms and non-traditional software elements. These aircraft will likely incorporate adaptive control algorithms that will provide enhanced safety, autonomy, and robustness during adverse conditions. Unmanned aircraft will operate alongside manned aircraft in the National Airspace (NAS), with intelligent software performing the high-level decision-making functions normally performed by human pilots. Even human-piloted aircraft will necessarily include more autonomy. However, there are serious barriers to the deployment of new capabilities, especially for those based upon software including adaptive control (AC) and artificial intelligence (AI) algorithms. Current civil aviation certification processes are based on the idea that the correct behavior of a system must be completely specified and verified prior to operation. This report by Rockwell Collins and SIFT documents our comprehensive study of the state of the art in intelligent and adaptive algorithms for the civil aviation domain, categorizing the approaches used and identifying gaps and challenges associated with certification of each approach

ABSTRACT

Dance games are one of the most popular types of bodycontrolled console games, making them ideal candidates for initiating exertion in players who do not exercise regularly. However, in order to become effective tools for consistent cardiovascular exercise, dance games need to maintain interest over a long time span. One solution that could help with long-term engagement is the addition of more narrative, competitive, and decorative elements. While other gameplay genres utilize this content to keep players involved, motion-controlled dance games are just beginning to incorporate these elements. We built Dance Enhanced, a website designed to offer earnable content to players of the game Dance Central 2. We conducted a four-week study comparing a group of participants playing the game alone with a group that also had access to the website. In this paper, we discuss the methodology for designing and operating this study, as well as our results, which indicated the potential for higher interest in competition, characters and storylines when presented with extra content

Chronic Exposure to Malaria Is Associated with Inhibitory and Activation Markers on Atypical Memory B Cells and Marginal Zone-Like B Cells

In persistent infections that are accompanied by chronic immune activation, such as human immunodeficiency virus, hepatitis C virus, and malaria, there is an increased frequency of a phenotypically distinct subset of memory B cells lacking the classic memory marker CD27 and showing a reduced capacity to produce antibodies. However, critical knowledge gaps remain on specific B cell changes and immune adaptation in chronic infections. We hypothesized that expansion of atypical memory B cells (aMBCs) and reduction of activated peripheral marginal zone (MZ)-like B cells in constantly exposed individuals might be accompanied by phenotypic changes that would confer a tolerogenic profile, helping to establish tolerance to infections. To better understand malaria-associated phenotypic abnormalities on B cells, we analyzed peripheral blood mononuclear cells from 55 pregnant women living in a malaria-endemic area of Papua Nueva Guinea and 9 Spanish malaria-naïve individuals using four 11-color flow cytometry panels. We assessed the expression of markers of B cell specificity (IgG and IgM), activation (CD40, CD80, CD86, b220, TACI, and CD150), inhibition (PD1, CD95, and CD71), and migration (CCR3, CXCR3, and CD62l). We found higher frequencies of active and resting aMBC and marked reduction of MZ-like B cells, although changes in absolute cell counts could not be assessed. Highly exposed women had higher PD1+-, CD95+-, CD40+-, CD71+-, and CD80+-activated aMBC frequencies than non-exposed subjects. Malaria exposure increased frequencies of b220 and proapoptotic markers PD1 and CD95, and decreased expression of the activation marker TACI on MZ-like B cells. The increased frequencies of inhibitory and apoptotic markers on activated aMBCs and MZ-like B cells in malaria-exposed adults suggest an immune-homeostatic mechanism for maintaining B cell development and function while simultaneously downregulating hyperreactive B cells. This mechanism would keep the B cell activation threshold high enough to control infection but impaired enough to tolerate it, preventing systemic inflammation

Employees’ feelings about more meetings: An overt analysis and recommendations for improving meetings

Purpose – The purpose of this paper is to identify how employees feel about having more meetings and what can be done to improve employees’ feelings about their work meetings. Design/methodology/approach – Data were obtained from three samples of working adults. The first was a convenience sample recruited by undergraduate students (n = 120), the second was a stratified random sample from a metropolitan area in the southern USA (n = 126), and the third was an internet-based panel sample (n = 402). Constant comparative analysis of responses to open-ended questions was used to investigate the overarching research questions. Findings – It is found that employees enjoy meetings when they have a clear objective, and when important relevant information is shared. Consistent with conservation of resources theory, most employees are unhappy with meetings when they reduce their work-related resources (e.g. meetings constrain their time, lack structure and are unproductive). Practical implications – The data suggest that meetings appear to be both resource-draining and resource-supplying activities in the workplace. Researchers and managers should consider overtly asking about how people feel about meetings, as a means of identifying areas for future research inquiry and targets for improvement in the workplace generally. Originality/value – The paper describes one of the few studies on meetings that ask the participants overtly what their feelings are regarding their workplace meetings. Additionally, the paper illustrates the usefulness of qualitative data analysis as a means for further understanding workplace activities viewing respondents as informants. Keywords United States of America, Employees behaviour, Employees attitudes, Employees participation, Meetings, Meeting demands, Qualitative research, Thematic analysi

Outbreaks of Pneumocystis Pneumonia in 2 Renal Transplant Centers Linked to a Single Strain of Pneumocystis: Implications for Transmission and Virulence

By restriction fragment length polymorphism analysis, 2 outbreaks of Pneumocystis pneumonia in renal transplant patients in Europe were shown to be caused by the same strain of Pneumocystis; another outbreak in Japan was caused by a different strai