1,884 research outputs found

    Structural design options for the new 34 meter beam waveguide antenna

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    In addition to the successful network of 34 m High Efficiency antennas recently built by JPL, the Deep Space Network (DSN) is embarking on the construction of a 34 m high performance, research and development antenna with beam waveguide optics at the Venus site. The construction of this antenna presents many engineering challenges in the area of structural, mechanical, RF, and pointing system design. A set of functional and structural design requirements is outlined to guide analysts in the final configuration selection. Five design concepts are presented covering both the conventional center-fed beam optics as well as the nonconventional, by-pass beam configuration. The merits of each concept are discussed with an emphasis on obtaining a homologous design. The preliminary results of structural optimization efforts, currently in progress, are promising, indicating the feasibility of meeting, as a minimum, all X-band (8.4 GHz) requirements, with a goal towards meeting Ka-band (32 GHz) quality performance, at the present budget constraints

    Tree Buffers

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    In runtime verification, the central problem is to decide if a given program execution violates a given property. In online runtime verification, a monitor observes a program’s execution as it happens. If the program being observed has hard real-time constraints, then the monitor inherits them. In the presence of hard real-time constraints it becomes a challenge to maintain enough information to produce error traces, should a property violation be observed. In this paper we introduce a data structure, called tree buffer, that solves this problem in the context of automata-based monitors: If the monitor itself respects hard real-time constraints, then enriching it by tree buffers makes it possible to provide error traces, which are essential for diagnosing defects. We show that tree buffers are also useful in other application domains. For example, they can be used to implement functionality of capturing groups in regular expressions. We prove optimal asymptotic bounds for our data structure, and validate them using empirical data from two sources: regular expression searching through Wikipedia, and runtime verification of execution traces obtained from the DaCapo test suite

    Monitoring Partially Synchronous Distributed Systems using SMT Solvers

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    In this paper, we discuss the feasibility of monitoring partially synchronous distributed systems to detect latent bugs, i.e., errors caused by concurrency and race conditions among concurrent processes. We present a monitoring framework where we model both system constraints and latent bugs as Satisfiability Modulo Theories (SMT) formulas, and we detect the presence of latent bugs using an SMT solver. We demonstrate the feasibility of our framework using both synthetic applications where latent bugs occur at any time with random probability and an application involving exclusive access to a shared resource with a subtle timing bug. We illustrate how the time required for verification is affected by parameters such as communication frequency, latency, and clock skew. Our results show that our framework can be used for real-life applications, and because our framework uses SMT solvers, the range of appropriate applications will increase as these solvers become more efficient over time.Comment: Technical Report corresponding to the paper accepted at Runtime Verification (RV) 201

    Presentations to an urban emergency department in Bern, Switzerland associated with acute recreational drug toxicity

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    Although the recreational use of psychoactive substances is common there is only limited systematic collection of data on acute drug toxicity or hospital presentations. Currently, data from Switzerland are only available from the University Hospital of Basel. The present study aimed to describe the presentations due to recreational drug use at an emergency department in Bern, Switzerland during a 4 year period.; Retrospective analysis of cases presenting from May 2012 to April 2016 at the emergency department of the University Hospital of Bern, Switzerland, with symptoms/signs consistent with acute toxicity of recreational drug use. The cases were retrieved using a comprehensive full-text search algorithm of the electronic health records. Isolated ethanol intoxications were excluded.; During the study period, 503 of the 157,328 emergency department attendances were directly related to acute toxicity of substances used recreationally. The mean patient age was 33 years (range 16-74), 68% were male. Alcohol co-ingestion was reported in 54% of the cases, and use of more than one recreational drug in 37% of the cases. Most presentations were related to cocaine (29%), cannabis (26%), heroin (20%) and benzodiazepines/sedatives (18%). Urine drug screening immunoassay was available in 277 cases (55%). The most frequently detected substances were cannabis (29%), cocaine (22%), benzodiazepines (21%) and opioids excluding methadone (20%). There were only two intoxications with novel psychoactive substances (NPSs): One with methylone and one with 2,5-dimethoxy-4(n)-propylphenethylamine (2C-P). The majority of patients (58%) displayed impaired consciousness (Glasgow Coma Scale (GCS) <15) upon presentation and/or pre-hospital; 21% were unconscious (GCS <8). Other frequent symptoms were agitation (36%), tachycardia (29%), and anxiety (24%). Severe complications included two fatalities, three acute myocardial infarctions, two intracranial haemorrhages, as well as psychosis and seizures in 71 and 26 cases, respectively.; Most medical problems related to recreational drug use were associated with cocaine and cannabis use and were mainly characterised by central nervous system depression, sympathomimetic toxicity and/or psychiatric disorders. Presentations related to acute toxicities of NPSs appear to be uncommon, while prescription drugs were after classical recreational drugs the substances most commonly reported

    Citizen advisory groups for the creation and improvement of decision aids: experience from two Swiss centers for primary care.

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    Guidelines for patient decision aids (DA) recommend target population involvement throughout the development process, but developers may struggle because of limited resources. We sought to develop a feasible means of getting repeated feedback from users. Between 2017 and 2020, two Swiss centers for primary care (Lausanne and Bern) created citizen advisory groups to contribute to multiple improvement cycles for colorectal, prostate and lung cancer screening DAs. Following Community Based Participatory Research principles, we collaborated with local organizations to recruit citizens aged 50 to 75 without previous cancer diagnoses. We remunerated incidental costs and participant time. One center supplemented in-person meetings by mailed paper questionnaires, while the other supplemented meetings using small-group workshops and analyses of meeting transcripts. In Lausanne, we received input from 49 participants for three DAs between 2017 and 2020. For each topic, participants gave feedback on the initial draft and 2 subsequent versions during in-person meetings with ~ 8 participants and one round of mailed questionnaires. In Bern, 10 participants were recruited among standardized patients from the university, all of whom attended in-person meetings every three months between 2017 and 2020. At both sites, numerous changes were made to the content, appearance, language, and tone of DAs and outreach materials. Participants reported high levels of satisfaction with the participative process. Citizen advisory groups are a feasible means of repeatedly incorporating end-user feedback during the creation of multiple DAs. Methodological differences between the two centers underline the need for a flexible model adapted to local needs
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