Search for > 200 TeV photons from Cygnus X-3 in 1988 and 1989

Journal ArticleOver a period of 16 months from April 1988 to August 1989, we have monitored the flux of cosmic-ray showers with energies above 2X 10^14 eV. We used a two-level array of scintillators covering an area of 3 X 10^4 m2 . Counters on the surface measure the size and direction of each shower while counters buried 3 m beneath the surface sample the muons. By selecting showers with relatively few muons (less than one-tenth the average) the background of hadron-induced showers should be reduced by a factor of 150 or more while showers started by y rays should not be affected by this cut. We find no evidence for an excess from the direction of Cygnus X-3 either in ordinary showers or in muon-poor showers. For energies above 2X 10^14 eV, with 90% confidence, we find the excess flux of cosmic rays from the direction of Cygnus X-3 to be less than 1.3X 10^-13 cm-2s-1 and the flux of photons (assuming they produce muon-poor showers) to be less than 1.5X10^-14 cm-V. This limit is substantially below the level of signals reported by earlier work. The period of observation included the intense radio bursts of June and July 1989. A portion of the data covering the 77-day period surrounding these events also showed no evidence for an excess

Search for y rays above 10^14 eV from Cygnus X-3 during the June and July 1989 radio outbursts

Journal ArticleWe have looked for γ-ray emission above 100 TeV from the binary x-ray source Cygnus X-3 during a period of intense radio emission in the summer of 1989. We find no evidence for excess air showers from the direction of the source and the muon content of air showers from this direction is the same as that of ordinary cosmic rays. The flux of γ rays from Cyguns X-3 with energies exceeding 2.1 X 10^14 eV is <5.5 X 10^-13cm-1 sec -1 (90%C.L.)

Search for > 200 TeV photons from Cygnus X-3 in 1988 and 1989

Journal ArticleOver a period of 16 months from April 1988 to August 1989, we have monitored the flux of cosmic-ray showers with energies above 2X 101 4 eV. We used a two-level array of scintillators covering an area of 3 X 104 m2. Counters on the surface measure the size and direction of each shower while counters buried 3 m beneath the surface sample the muons

Search for compact sources of cosmic photons above 200 TeV

Journal ArticleFrom April 1988 to February 1990 we used a two-level array of scintillators to search in the cosmic radiation for compact sources of y rays above 200 TeV. Counters on the surface measured the size and direction of extensive air showers while counters buried 3 m below ground measured their muon content. Showers induced by y rays are expected to have many fewer muons than those initiated by hadrons so the selection of muon-poor showers should greatly reduce the background of hadronic showers. Three objects, Cygnus X-3, the Crab nebula, and Hercules X-l, were examined in detail. Searches were made on short and long time scales and source periodicity was used, where applicable, to enhance any possible signals. We found no evidence for any compact sources

Search for γ rays above 1014 eV from Cygnus X-3 during the June and July 1989 radio outbursts

Journal ArticleWe have looked for γ-ray emission above 100 TeV from the binary x-ray source Cygnus X-3 during a period of intense radio emission in the summer of 1989. We find no evidence for excess air showers from the direction of the source and the muon content of air showers from this direction is the same as that of ordinary cosmic rays. The flux of γ rays from Cygnus X-3 with energies exceeding 2.1x10^14 eV is < 5.5x10^-13 cm-1 sec-1 (90% C.L.)

Search for compact sources of cosmic photons above 200 TeV

Journal ArticleFrom April 1988 to February 1990 we used a two-level array of scintillators to search in the cosmic radiation for compact sources of y rays above 200 TeV. Counters on the surface measured the size and direction of extensive air showers while counters buried 3 m below ground measured their muon content. Showers induced by y rays are expected to have many fewer muons than those initiated by hadrons so the selection of muon-poor showers should greatly reduce the background of hadronic showers

Correction to: The vibrations induced by surface irregularities in road pavements – a Matlab® approach

After publication of this article [1], it is noticed the article contained an error with eq. 12, the c s should be squared. The correct eq. 12 is provided below

The vibrations induced by surface irregularities in road pavements – a Matlab® approach

n/

A model-based rams estimation methodology for innovative aircraft on-board systems supporting mdo applications

The reduction of aircraft operating costs is one of the most important objectives addressed by aeronautical manufactures and research centers in the last decades. In order to reach this objective, one of the current ways is to develop innovative on-board system architectures, which can bring to lower fuel and maintenance costs. The development and optimization of these new aircraft on-board systems can be addressed through a Multidisciplinary Design Optimization (MDO) approach, which involves different disciplines. One relevant discipline in this MDO problem is Reliability, Availability, Maintainability and Safety (RAMS), which allows the assessment of the reliability and safety of aircraft systems. Indeed the development of innovative systems cannot comply with only performance requirements, but also with reliability and safety constraints. Therefore, the RAMS discipline plays an important role in the development of innovative on-board systems. In the last years, different RAMS models and methods have been defined, considering both conventional and innovative architectures. However, most of them rely on a document-based approach, which makes difficult and time consuming the use of information gained through their analysis to improve system architectures. On the contrary, a model-based approach would make easier and more accessible the study of systems reliability and safety, as explained in several studies. Model Based Systems Engineering (MBSE) is an emerging approach that is mainly used for the design of complex systems. However, only a few studies propose this approach for the evaluation of system safety and reliability. The aim of this paper is therefore to propose a MBSE approach for model-based RAMS evaluations. The paper demonstrates that RAMS models can be developed to quickly and more effectively assess the reliability and safety of conventional and innovative on-board system architectures. In addition, further activities for the integration of the model-based RAMS methodology within MDO processes are described in the paper

ASSESSMENT OF NEW TECHNOLOGIES IN A MULTI-DISCIPLINARY DESIGN ANALYSIS AND OPTIMIZATION ENVIRONMENT INCLUDING RAMS AND COST DISCIPLINES

The aim of the present paper is to assess the effect of new technologies on the whole aircraft product including its costs, reliability and maintainability characteristics. Several studies have been conducted dealing with the preliminary evaluation of Reliability, Availability, Maintainability and Safety (RAMS) of conventional aircraft. They provide a very effective method to preliminary estimate RAMS characteristics but their employment is not completely suitable for the analysis of unconventional configurations adopting new technologies. This paper aims at evaluating how the aircraft costs and RAMS characteristics are affected by new structures material, natural laminar flow wing technology and unconventional actuator system (electro-hydrostatic actuators), hence an update of the state of the art models is needed. This evaluation is performed by means of a setup and execution of a Multidisciplinary Design Analysis and Optimization (MDAO) workflow. The MDAO environment includes the aircraft conceptual design, aircraft performance, structure design, engine design, on-board systems design, RAMS and maintenance cost modules. The RAMS module is used to obtain the failure rates and maintenance effort (in terms of maintenance man hour per flight hour) at subsystem level. The cost module is based on a new maintenance cost model able to estimate the operating cost of the different aircraft variants. The selected new technologies are applied to a regional jet developed within the framework of AGILE research project. For each technology, a different variant of this aircraft is analyzed. Results show that some important saves are reached both in terms of maintenance and fuel cost when new technologies are applied