Properties of categories enriched over the category of metric spaces are investigated and applied to a study of well-known constructions of metric and Banach spaces. We prove e.g. that weighted ...limits and colimits exist in a metric-enriched category iff ordinary limits and colimits exist and ε-(co)equalizers are given by ε-(co)isometries for all ε.
An object is called approximately injective w.r.t. a morphism h:A→A′ iff morphisms from A into it are arbitrarily close to those morphisms that factorize through h. We investigate classes of objects specified by their approximate injectivity w.r.t. given morphisms. They are called approximate-injectivity classes. And we also study, conversely, classes of morphisms specified by the property that certain objects are approximately injective w.r.t. them.
For every class of morphisms satisfying a mild smallness condition we prove that the corresponding approximate-injectivity class is weakly reflective, and we study the properties of the reflection morphisms. As an application we present a new categorical proof of the essential uniqueness of the Gurarii space.
Abstract
One of the remaining challenges in magnetic thermonuclear fusion is survival of the heat shield protecting the tokamak reactor vessel against excessive plasma heat fluxes. Unmitigated high ...confinement edge localized mode (ELM) is a regular heat pulse damaging the heat shield. We suggest a novel concept of magnetic sweeping of the plasma contact strike point fast and far enough in order to spread this heat pulse. We demonstrate feasibility of a dedicated copper coil in a resonant circuit, including the induced currents and power electronics. We predict the DEMO ELM properties, simulate heat conduction, 3D particles motion and magnetic fields of the plasma and coil in COMSOL Multiphysics and Matlab. The dominant system parameter is voltage, feasible 18 kV yields 1 kHz sweeping frequency, suppressing the ELM-induced surface temperature rise by a factor of 3. Multiplied by other known mitigation concepts, ELMs might be mitigated enough to ensure safe operation of DEMO.
It is well known that classical varieties of
$\Sigma$
-algebras correspond bijectively to finitary monads on
$\mathsf{Set}$
. We present an analogous result for varieties of ordered
$\Sigma$
...-algebras, that is, categories of algebras presented by inequations between
$\Sigma$
-terms. We prove that they correspond bijectively to strongly finitary monads on
$\mathsf{Pos}$
. That is, those finitary monads which preserve reflexive coinserters. We deduce that strongly finitary monads have a coinserter presentation, analogous to the coequalizer presentation of finitary monads due to Kelly and Power. We also show that these monads are liftings of finitary monads on
$\mathsf{Set}$
. Finally, varieties presented by equations are proved to correspond to extensions of finitary monads on
$\mathsf{Set}$
to strongly finitary monads on
$\mathsf{Pos}$
.
Given the known carcinogenic effects, asbestos minerals are considered as general health hazard. Therefore, the elimination of asbestos materials from the environment is necessary. Asbestos minerals ...should be entirely transformed to a non-hazardous material. One of these methods is destructing the fibers structure of asbestos minerals by thermal treatment. Asbestos minerals are naturally occurring hydrous silicates, so that they decompose to release water by heating at high temperatures which may lead to changes in crystal structure and the formation of new phases without the dangerous properties. In this article, thermal behavior of asbestos minerals is investigated to observe the disappearance of this hazardous structure and to characterize products obtained by this way. Ten samples of asbestos minerals (six chrysotile samples from different locations, two samples of crocidolite, one amosite, and one tremolite) from different locations were tested. Mineralogical and morphological data (X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy) were obtained before and after differential thermal analysis.
A new high heat flux ball-pen probe head installed on the midplane manipulator is currently being used in ASDEX-Upgrade (AUG). The probe was designed to withstand high heat fluxes making possible the ...investigation of the plasma edge under harsh conditions, such as low power H-mode. Composed of seven pins (four Langmuir probes, mounted in two Mach probe pairs, and three ball-pen probes), the new probe head allows us to measure several plasma parameters simultaneously and with high temporal resolution. A novel method to correct the sheath potential dynamically accounting for the total secondary electron emission is introduced together with applications to obtain the electron temperature and plasma potential profiles. The total secondary electron emission yield is obtained from particle in cell simulations in AUG condition and probe realistic impact angle with respect to the magnetic field. Finally, the probe capability to investigate turbulence around the separatrix of AUG is discussed.
Sv 07Kh25N13 is austenitic stainless steel used in nuclear industry. Due to its excellent corrosion resistance in the environment of WWER type nuclear reactor primary circuit, it is applied as ...anticorrosive cladding of the reactor pressure vessel. In this paper, results of detailed experimental research of failure behaviour of the cladding are presented. Static fracture toughness values J0.2 exhibited an extreme scatter. Metallographic analysis performed on the fractured specimens revealed large variations of structure within every single cladding layer. Fractographic analysis performed on fracture surfaces revealed considerable variations of micromechanisms taking place during ductile crack propagation. Conclusions on the relationship between the local microstructure, the failure mode and the fracture toughness of the cladding were drawn. Results indicate that the fracture toughness of the cladding was primarily determined by local amount of sigma phase in the area of crack propagation.
•Fracture toughness (J0.2) of WWER RPV cladding exhibited an extreme scatter.•Cladding had complicated duplex austenitic-ferritic solidification structure.•Presence of sigma phase was determined in solidification cells and dendrites.•Sigma particles caused an extreme degradation of ductile tearing strength.
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