PMMA – C60 composite: thermal decomposition experiments in mass spectrometer and quantum chemical modeling

Mass-spectrometric thermal decomposition experiments with submicron films of neat polymethylmethacrylate (PMMA), and PMMA-fullerene composite (PMMA-C60) after UV irradiation are discussed. The experiment registers thermal desorption mass spectra (TDMS), that is the monomer desorption rate versus time upon gradual heating the PMMA films in a given heating regime. The spectra provide information on the amount of the monomer desorbed at different decomposition stages upon heating the given amount of film material as well as on the spectral shape changes. It is shown that both amount of monomer and the TDMS spectral shape are sensitive to the presence of fullerene and UV irradiation. The experimental results are discussed in terms of quantum chemical models of binding. The DFT/B3LYP-D3/def2/J RIJCOSX level of theory was used. The MMA-C60 structures which can yield different amounts of monomer have been compared.

Really Trapped in the Heat?

This paper aims to account for the role of occupants' efforts in reducing the space-heating costs of panel apartments linked to district heating systems. We present the findings of a questionnaire survey among residents of North-West Budapest (Hungary). Our results show that the roles of efforts are limited in the panel housing context, but wider access to appropriate information on those (limited) opportunities could significantly alleviate the burden on households trapped in an inadequate space heating regime.

Prerequisites for the Calculation of Natural Lighting of Premises Taking into Account the Insolation Component in the Region of Equatorial Latitudes

To solve the problem of designing buildings with taking into account modern hygienic and technical requirements, it is of great importance to take into account the factors of the natural and climatic environment, in which the radiant energy of the sun plays an important role, determining the insolation-lighting-heating regime of the premises. The natural lighting of the premises is studied and the prerequisites for the refinement and development of the methodology for calculating the natural indoor lighting of the premises taking into account the insolation conditions for a specific region of the equatorial countries are formulated. Proposals for improving the methodology for calculating the daylighting in the room, taking into account the insolation components, have been developed.

Post-Fire Susceptibility to Brittle Fracture of Selected Steel Grades Used in Construction Industry—Assessment Based on the Instrumented Impact Test

The change in the value of the breaking energy is discussed here for selected steel grades used in building structures after subjecting the samples made of them to episodes of heating in the steady-state heating regime and then cooling in simulated fire conditions. These changes were recorded based on the instrumented Charpy impact tests, in relation to the material initial state. The S355J2+N, 1H18N9T steels and also X2CrNiMoN22-5-3 duplex steel were selected for detailed analysis. The fire conditions were modelled experimentally by heating the samples and then keeping them for a specified time at a constant temperature of: 600 °C (first series) and 800 °C (second series), respectively. Two alternative cooling variants were investigated in the experiment: slow cooling of the samples in the furnace, simulating the natural fire progress, without any external extinguishing action and cooling in water mist simulating an extinguishing action by a fire brigade. The temperature of the tested samples was set at the level of −20 °C and alternatively at the level of +20 °C. The conducted analysis is aimed at assessing the risk of sudden, catastrophic fracture of load-bearing structure made of steel degraded as a result of a fire that occurred previously with different development scenarios.

Post-Fire Susceptibility to Brittle Fracture of Selected Steel Grades Used in Construction Industry – Assessment Based on the Instrumented Impact Test

The change in the value of the breaking energy is discussed here for selected steel grades used in building structures after subjecting the samples made of them to episodes of heating in the steady-state heating regime and then cooling in a simulated fire conditions. These changes were recorded based on the instrumented Charpy impact tests, in relation to the material initial state. The S355J2+N, 1H18N9T steels and also X2CrNiMoN22-5-3 duplex steel were selected for detailed analysis. The fire conditions were modelled experimentally by heating the samples and then keeping them for a specified time at a constant temperature of: 600°C (first series) and 800°C (second series), respectively. Two alternative cooling variants were investigated in the experiment: slow cooling of the samples in the furnace, simulating the natural fire progress, without any external extinguishing action, and cooling them in water mist simulating an extinguishing action by a fire brigade. The temperature of the tested samples was set at the level -20oC and alternatively at the level + 20oC. The conducted analysis is aimed at assessing the risk of sudden, catastrophic fracture of load-bearing structure made of steel degraded as a result of a fire previously occurred with different development scenarios.

Floquet conformal field theories with generally deformed Hamiltonians

In this work, we study non-equilibrium dynamics in Floquet conformal field theories (CFTs) in 1+1D, in which the driving Hamiltonian involves the energy-momentum density spatially modulated by an arbitrary smooth function. This generalizes earlier work which was restricted to the sine-square deformed type of Floquet Hamiltonians, operating within a \mathfrak{sl}_2𝔰𝔩2 sub-algebra. Here we show remarkably that the problem remains soluble in this generalized case which involves the full Virasoro algebra, based on a geometrical approach. It is found that the phase diagram is determined by the stroboscopic trajectories of operator evolution. The presence/absence of spatial fixed points in the operator evolution indicates that the driven CFT is in a heating/non-heating phase, in which the entanglement entropy grows/oscillates in time. Additionally, the heating regime is further subdivided into a multitude of phases, with different entanglement patterns and spatial distribution of energy-momentum density, which are characterized by the number of spatial fixed points. Phase transitions between these different heating phases can be achieved simply by changing the duration of application of the driving Hamiltonian. %In general, there are rich internal structures in the heating phase characterized by different numbers of spatial fixed points, which result in different entanglement patterns and distribution of energy-momentum density in space. %Interestingly, after each driving cycle, these spatial fixed points will shuffle to each other in the array, and come back to the original locations after pp (p\ge 1p≥1) driving cycles. We demonstrate the general features with concrete CFT examples and compare the results to lattice calculations and find remarkable agreement.

Optimizing Induction Heating of WNiCo Billets Processed via Intensive Plastic Deformation

The aim of the work is to optimize the induction heating regime and propose a suitable deformation temperature for a pre-sintered powder-based tungsten heavy alloy workpiece subsequently processed via rotary swaging. The heating regime is designed with the help of numerical analyses and subsequent experiments. The first part of the study focuses on the theoretic background of the induction heating and comprises the development of a reliable induction heating model via performing electromagnetic simulations in two individual computational software packages (for verification). The second part of the study then involves the optimization of the heating regime using the designed numerical model. Last but not least, the predicted results are compared to the experimentally acquired results, and the optimized heating regime, applicable before experimental rotary swaging of the WNiCo workpiece, is proposed. The results of the microstructure analyses of the workpiece heated to the selected optimum deformation temperature of 900 °C showed that the designed induction heating procedure provided sufficient heating of the bulk of the workpiece (contrary to the lower swaging temperature), as the swaged microstructure featured well-deformed tungsten agglomerates. Furthermore, the analyses documented the high-quality oxidation-free surface of the particular workpiece (contrary to the higher swaging temperature).