97 research outputs found
Принципы построения сетевых систем обнаружения вторжений на базе ПЛИС
The common principles of FPGA-based NIDS (Network Intrusion Detection
Systems) construction are investigated. The main requirements and characteristics of
such systems are discussed. The generalized structure of a reconfigurable NIDS is
described
Анализ способов и устройств для уплотнения мелкофракционных шихт
Выполнен анализ способов уплотнения мелкофракционных сыпучих
материалов. Предложена схема уплотнения на основе валковых прессов с
многоступенчатым уплотнением
Magnetic Fields, Relativistic Particles, and Shock Waves in Cluster Outskirts
It is only now, with low-frequency radio telescopes, long exposures with
high-resolution X-ray satellites and gamma-ray telescopes, that we are
beginning to learn about the physics in the periphery of galaxy clusters. In
the coming years, Sunyaev-Zeldovich telescopes are going to deliver further
great insights into the plasma physics of these special regions in the
Universe. The last years have already shown tremendous progress with detections
of shocks, estimates of magnetic field strengths and constraints on the
particle acceleration efficiency. X-ray observations have revealed shock fronts
in cluster outskirts which have allowed inferences about the microphysical
structure of shocks fronts in such extreme environments. The best indications
for magnetic fields and relativistic particles in cluster outskirts come from
observations of so-called radio relics, which are megaparsec-sized regions of
radio emission from the edges of galaxy clusters. As these are difficult to
detect due to their low surface brightness, only few of these objects are
known. But they have provided unprecedented evidence for the acceleration of
relativistic particles at shock fronts and the existence of muG strength fields
as far out as the virial radius of clusters. In this review we summarise the
observational and theoretical state of our knowledge of magnetic fields,
relativistic particles and shocks in cluster outskirts.Comment: 34 pages, to be published in Space Science Review
Scanning electron microscope-cathodoluminescence (SEM-CL) imaging of planar deformation features and tectonic deformation lamellae in quartz
Planar deformation features (PDFs) in quartz are essential proof for the correct
identification of meteorite impact structures and related ejecta layers, but can be confused
with tectonic deformation lamellae. The only completely reliable method to demonstrate the
shock origin of suspected (sub-) planar microstructures, transmission electron microscope
(TEM) observations, is costly and time consuming. We have used a cathodoluminescence
(CL) detector attached to a scanning electron microscope (SEM) to image both PDFs and
tectonic deformation lamellae in quartz to demonstrate the potential of a simple method to
identify PDFs and define characteristics that allow their distinction from tectonic
deformation lamellae. In both limited wavelength grayscale and composite color SEM-CL
images, PDFs are easily identified. They are straight, narrow, well-defined features, whereas
tectonic deformation lamellae are thicker, slightly curved, and there is often no clear
boundary between lamella and host quartz. Composite color images reveal two types of CL
behavior in PDFs: either they emit a red to infrared CL signal or they are nonluminescent.
The color of the CL signal emitted by tectonic deformation lamellae ranges from blue to red.
For comparison, we also imaged several shocked quartz grains at cryogenic temperature. In
most cases, the PDF characteristics in cryo-CL images do not differ significantly from those
in images recorded at room temperature. We conclude that SEM-CL imaging, especially
when color composites are used, provides a promising, practical, low cost, and nondestructive
method to distinguish between PDFs and tectonic lamellae, even when the simplest CL
techniques available are used
Shocked quartz in the SEM: Distinction between amorphous and healed PDFs
Combined SEM techniques show that different CL signatures of PDFs are related to fresh and healed microstructures of PDFs and host quartz. This is confirmed by TEM results. A combination of SEM techniques can give the same type of information as TE
The Guarda structure (Portugal): Impact structure or not? Microstructural studies of Quartz, Zircon and Monazite
The Guarda Structure in north-eastern Portugal has been proposed as a potential impact structure. We have studied the structure in detail, but no field or microscopic evidence has been found to support the impact hypothesi
The Othris Ophiolite, Greece: A snapshot of subduction initiation at a mid-ocean ridge
The mantle section of the Tethyan-type Othris Ophiolite, Greece, records tectono-magmatic processes characteristic of both mid-ocean ridges and supra-subduction zones. The Othris Ophiolite is a remnant of the Jurassic Neotethys Ocean, which existed between Eurasia and Gondwanaland. Othris peridotites range from fertile plagioclase lherzolites to depleted harzburgites. Abundances of A
Upper mantle viscosity and lithospheric thickness under Iceland
Deglaciation during the Holocene on Iceland caused uplift due to glacial isostatic adjustment. Relatively
low estimates for the upper mantle viscosity and lithospheric thickness result in rapid uplift responses to
the deglaciation cycles on Iceland. The relatively high temperatures of the upper mantle under the newly
formed mid-ocean ridge under Iceland are responsible for the low upper mantle viscosity values. In this
study, estimates for lithospheric thickness and upper mantle viscosity under Iceland from glacial isostatic
adjustment studies are complemented by a microphysical modelling approach using the theoretical
temperature distribution under mid-ocean ridges combined with olivine diffusion and dislocation creep
flow laws. The lithospheric thickness (27–40 km) and upper mantle viscosity (2
×
1018–1019 Pa s) outcomes
for the upper mantle recent glaciation under the Vatnajökull glacier are consistent with previous
reports of viscosity and lithospheric thickness from glacial isostatic adjustment studies. A combination
of a 40 km thick elastic lithosphere and an average upper mantle viscosity of 5
×1018 Pa s would suggest
that the upper mantle under Iceland is most likely dry. The earlier and larger Weichselian glaciation
event (∼10,000 BP) on Iceland is predicted to have had a slightly larger upper mantle viscosity
∼1019 Pa s
and a lithospheric thickness of
∼100 km. Large lateral variations in upper mantle viscosity and especially
lithospheric thickness are expected for Iceland perpendicular to the ridge axis
Upper mantle viscosity and lithospheric thickness under Iceland
Deglaciation during the Holocene on Iceland caused uplift due to glacial isostatic adjustment. Relatively
low estimates for the upper mantle viscosity and lithospheric thickness result in rapid uplift responses to
the deglaciation cycles on Iceland. The relatively high temperatures of the upper mantle under the newly
formed mid-ocean ridge under Iceland are responsible for the low upper mantle viscosity values. In this
study, estimates for lithospheric thickness and upper mantle viscosity under Iceland from glacial isostatic
adjustment studies are complemented by a microphysical modelling approach using the theoretical
temperature distribution under mid-ocean ridges combined with olivine diffusion and dislocation creep
flow laws. The lithospheric thickness (27–40 km) and upper mantle viscosity (2
×
1018–1019 Pa s) outcomes
for the upper mantle recent glaciation under the Vatnajökull glacier are consistent with previous
reports of viscosity and lithospheric thickness from glacial isostatic adjustment studies. A combination
of a 40 km thick elastic lithosphere and an average upper mantle viscosity of 5
×1018 Pa s would suggest
that the upper mantle under Iceland is most likely dry. The earlier and larger Weichselian glaciation
event (∼10,000 BP) on Iceland is predicted to have had a slightly larger upper mantle viscosity
∼1019 Pa s
and a lithospheric thickness of
∼100 km. Large lateral variations in upper mantle viscosity and especially
lithospheric thickness are expected for Iceland perpendicular to the ridge axis
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