2,318 research outputs found
Near-optimal continuous patrolling with teams of mobile information gathering agents
No full textAutonomous unmanned vehicles equipped with sensors are rapidly becoming the de facto means of achieving situational awareness — the ability to make sense of, and predict what is happening in an environment. Particularly in environments that are subject to continuous change, the use of such teams to maintain accurate and up-to-date situational awareness is a challenging problem. To perform well, the vehicles need to patrol their environment continuously and in a coordinated manner.To address this challenge, we develop a near-optimal multi-agent algorithm for continuously patrolling such environments. We first define a general class of multi-agent information gathering problems in which vehicles are represented by information gathering agents — autonomous entities that direct their activity towards collecting information with the aim of providing accurate and up-to-date situational awareness. These agents move on a graph, while taking measurements with the aim of maximising the cumulative discounted observation value over time. Here, observation value is an abstract measure of reward, which encodes the properties of the agents’ sensors, and the spatial and temporal properties of the measured phenomena. Concrete instantiations of this class of problems include monitoring environmental phenomena (temperature, pressure, etc.), disaster response, and patrolling environments to prevent intrusions from (non-strategic) attackers.In more detail, we derive a single-agent divide and conquer algorithm to compute a continuous patrol (an infinitely long path in the graph) that yields a near-optimal amount of observation value. This algorithm recursively decomposes the graph, until high-quality paths in the resulting components can be computed outright by a greedy algorithm. It then constructs a patrol by concatenating these paths using dynamic programming. For multiple agents, the algorithm sequentially computes patrols for each agent in a greedy fashion, in order to maximise its marginal contribution to the team. Moreover, to achieve robustness, we develop algorithms for repairing patrols when one or more agents fail or the graph changes. For both the single and the multi-agent case, we give theoretical guarantees (lower bounds on the solution quality and an upper bound on the computational complexity in the size of the graph and the number agents) on the performance of the algorithms. We benchmark the single and multi-agent algorithm against the state of the art and demonstrate that it typically performs 35% and 33% better in terms of average and minimum solution quality respectively
Pseudomonas aeruginosa infections in children with cystic fibrosis : Determinants, detection and directed intervention
No full textPulmonary infections in children with CF are a major cause of morbidity and mortality. In particular, infections with P. aeruginosa lead to rapid pulmonary function decline and are hard to eradicate once established and adapted to the host environment. In this thesis, determinants of host- and bacterial factors for P. aeruginosa infections were investigated. Because of the possible benefit of early detection of P. aeruginosa with respect to eradication strategies, the diagnostic value of direct and indirect detection methods was examined. Also, interventions directed at prevention of initial P. aeruginosa infection by cycled antibiotic prophylaxis and directed at prevention of further pulmonary decline after establishment of P. aeruginosa infection by macrolide antibiotics were analysed. The major findings of this thesis are: -In CF pulmonary infection, the genetic diversity of P. aeruginosa isolates is lower than in P. aeruginosa isolates from infections in non-CF hosts. Clonal genotypes were observed in Dutch patients with CF, but not in patients without CF . -In CF, both eradicated and persistent initial colonising P. aeruginosa isolates show highly variable bacterial characteristics. It is not possible to predict persistence in the airways after initial P. aeruginosa colonisation by estimating these bacterial characteristics alone . -Increasing the culture frequency of oropharyngeal swabs enhances the diagnostic values for P. aeruginosa presence in the lower airways. -Serological measurements of specific anti-P. aeruginosa antibodies are sensitive in detecting chronic P. aeruginosa infections but do not yet contribute substantially in early detection of P. aeruginosa colonisation in the majority of children . -Cycled 3-monthly anti-Pseudomonas antibiotic prophylaxis does not prevent initial and persistent P. aeruginosa infection and subsequent lung function decline in children with CF. -Azithromycin therapy leads to a temporary pulmonary function improvement, but induces rapid macrolide resistance in S. aureus without significant decline in S. aureus isolation. -Transmission of macrolide-resistant S. aureus to household contacts of patients with CF was not proven
The Greece of the Greeks: By G.A. Perdicaris, A.M. Late Consul of the United Stats at Athens, in two volumes. New-York: Paine and Burgess, 1845.
No full textIntroduction: (introductory) by the authorDedication: by the author to those who are interested in the Fate of GreecePagination: PP21+293P, PP8+300P+1PPVolumes: 2Edition:1stText Genre:Prose / Journa
Automatic sign language recognition inspired by human sign perception
No full textAutomatic sign language recognition is a relatively new field of research (since ca. 1990). Its objectives are to automatically analyze sign language utterances. There are several issues within the research area that merit investigation: how to capture the utterances (cameras, magnetic sensors, instrumented gloves), how to extract interesting information from the captured data, and how to classify signs or sentences automatically using the extracted information. These issues are of an immediate and basic nature, and must be solved before any automatic recognition of sign language can be achieved. But other issues, pertaining to the nature of sign language and human recognition, are no less interesting: which elements of a sign are important for the meaning of an utterance? How do consecutive signs influence one another? Why are certain types of variation unimportant while others change the meaning of the sign? Automatic sign language recognition has, until recently, mostly focused on the first set of issues. In this thesis, we attempt to integrate knowledge about sign languages and human sign recognition into the automatic sign recognition process. Research on the (psycho)linguistics of sign languages is itself quite young (since ca. 1960), and many questions as yet unanswered. For this reason, we conduct our own studies of human sign language recognition. The knowledge gained from these experiments is applied in an existing automatic sign language recognition system. The thesis is divided into two parts: the first part describes the experiments conducted with human signers, the second part describes experiments investigating the possibilities of integrating such knowledge in the automatic recognizer. This recognizer is meant to be used in an interactive environment for young children to practice sign language vocabulary. For this reason, it is vision-based (which is unobtrusive), and only handles isolated signs. The experiments in part I of the thesis investigate the information content of various sign elements: fragments of a sign in time (chapter 2), and the sign aspects handshape and hand orientation (chapter 3). In time, the central phase of a sign is the most informative one, equally informative to the entire sign. Recognition based on other phases is also possible to a certain extent, and the transition from the preparation phase to the central phase appears to be a salient moment. As for the aspects, the aspect handshape proves more useful for recognition than hand orientation. Chapter 4 gives an overview of the human recognition research and discusses possibilities for application. In part II, the possibilities of utilizing the results of part I in the recognition system are investigated. Chapter 5 describes the addition of the handshape feature to the system (which chapter 3 showed to be the most interesting feature to add). Adding handshape gives a small improvement in the recognition performance. In chapter 6, the salience of the sign fragments used in chapter 2 for the automatic recognizer is investigated. The central phase proves to be the most informative one, as it was for human signers. Chapter 7 describes experiments in which a small set of frames is used to represent a sign. The results show a deterioration in recognition performance. Strict demands on the correctness of the remaining frames are probably partly responsible for the performance decrease. In conclusion, we can say that applying human knowledge in automatic sign language recognition is a complex task. Conclusions about human sign recognition do not necessarily hold for the automatic recognizer as well. The most important obstacles for utilizing information successfully seem to be: 1) data acquisition: computer vision is not as accomplished as human observers in capturing the complex, dynamic hand and face motions that form sign language. This means that information that is present in a sign movement for a human being may not be (correctly) observed by an automatic vision analysis system. Thus, the data that humans work with is not necessarily identical to the data the recognizer works with, and this may cause techniques that are successful for human signers to fail in the automatic system. And 2) differences in basic system architecture. Research into human sign recognition is still ongoing, there is no clear model of human sign recognition yet. This makes it more difficult to translate observations from human sign recognition to the automatic recognizer: human signers may use techniques that are not compatible with the current architecture of the recognizer. For example: human signers may process aspects independently. If the recognition system processes all data as a single stream, then such a technique cannot be implemented. A more thorough understanding of human sign recognition, more sophisticated computer vision techniques, and a close co-operation between the fields of automatic sign language recognition and human sign perception, seems the best way to overcome these obstacles.MediamaticsElectrical Engineering, Mathematics and Computer Scienc
Detection of Pseudomonas aeruginosa in patients with cystic fibrosis
No full textAbstractChronic pulmonary colonisation with Pseudomonas aeruginosa (PA) in patients with CF is associated with a high morbidity and mortality. Adequate treatment of first acquisition of PA might prevent or postpone chronic colonisation. Early detection of PA is therefore of major importance. Currently, cultures of oropharynx or sputum are most commonly practised. However, oropharyngeal culture has limitations both in the positive and negative predictive value for the presence of PA in the lower respiratory tract. Induction of sputum has little benefit in detection of PA. Serology might have additional value in early detection, when bacterial density is too low to be detected by culture. Molecular techniques are not yet widespread used for detection of PA, but have in general a high sensitivity. In this review, we describe the value of different diagnostic techniques for detecting PA
Improved pathogen detection in neonatal sepsis to boost antibiotic stewardship
No full textstatus: Publishe
Alle origini delle discipline aziendali: l’opera di G.A. Tagliente
No full textThe Contribution of G.A. Tagliente to the birth of business disciplines
The paper presents the work of a XVI century Italian Accounting author, G.A. Tagliente, giving a historiographic interpretation under a business economics point of view. The research is placed in a wider project of mapping Early Mod- ern Era contributions on Accounting, where contents, distinctly analyzed, are linked to their respective social and economic contexts. In the paper biograph- ical notes are placed in the Early XVI Century Venice and the whole literary production of the Author is presented before the proper accounting one. He was the second writer on double entry method, after Pacioli’s work. He pub- lished also books on mathematics for business, but his fortune is due mainly to the unique treatise on “simple entry book”, at those times very spread through the small and medium enterprises. Even if “minor” respect to the Great Pacioli, with him a cultural path began that would lead, finally, to the establish- ment of a new stream of thought: Accounting as we recognise it nowadays. In certain respects, furthermore, he underscored not still explored concern as- pects like family’s administration, extraordinary events, fixed assets and other peculiar issues
Reliable methods for predicting the sound from clustered rocket engines
No full textHigh area ratio rocket engines generate strong vibro-acoustic loads primarily during transient operations, like start-up and shut-down of the engine. These loads can adversely affect the launch vehicle and its payload. Thus, an accurate prediction of the loads produced during engine start-up is pertinent to the safety and reliability of the launch vehicle. The present work focuses on developing a robust framework for predicting these loads using laboratory scale rocket nozzles tested in the fully anechoic chamber at The Uni- versity of Texas at Austin. This encompasses corrections for the observer position relative to the prominent source region, as well as scaling factors to correct for geometric factors. The test campaign encompasses single, two, three and four nozzle clusters, as well as differences in nozzle geometry and operating conditions (nozzle pressure ratio)
Coming home to mother
No full textGift of Dr. Mary Jane Esplen.Piano vocal [instrumentation]We love to think of years ago [first line]We are coming home to Mother [first line of chorus]A flat [key]Piano [tempo]House, families, birds, photograph of M.E. Mollins [illustration]Popular song [form/genre]Publisher's advertisement on inside front [note]Mediatoon by G.A. Boyton [note
Working in soviet aircraft industry. Extract from G.A. Cheremukhin memories
No full textPublished by N.G. Georguiyeva
This is a publication of an excerpt from the G.A. Cheremukhin's memoirs «The work in the aircraft industry» (1921-2009). He was a famous aircraft designer noted both in Russia and abroad. This fragment contains the previously little known information on the beginning of the creation of a strategic bomber TU-4 in 1945-1947. N.G. Georgieva prepared this publication on the basis of the manuscript of his memoirs. The preface and footnotes contain biographic data on people who were mentioned in the memoirs and who were working together with the author of the memoirs
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