A qualitatively model to describe the influence of boundaries on the energy density by considering the energy leakage, and its extension on the system ventilation and fire fighting systems

Abstract In this paper constitutive models based on physical laws are derived that allow the energy flows and the release of energy to be described and predicted for fires in enclosed spaces and tunnels in particular. The models are generally formulated but are also specifically formulated for practical applications, e.g. for considering the effect of limited burning due to insufficient oxygen supply or the effect of fire fighting systems. The solutions agree with the experimentally obtained results in (Carvel et al, 2001 and Carvel et al, 2005). Accordingly, the methods and solutions derived here can be considered adequately validated

Comparison of cloud models for Brown Dwarfs

A test case comparison is presented for different dust cloud model approaches applied in brown dwarfs and giant gas planets. We aim to achieve more transparency in evaluating the uncertainty inherent to theoretical modelling. We show in how far model results for characteristic dust quantities vary due to different assumptions. We also demonstrate differences in the spectral energy distributions resulting from our individual cloud modelling in 1D substellar atmosphere simulationsComment: 5 pages, Proceeding to "Exoplantes: Detection, Formation, Dynamics", eds. Ferraz-Mello et

A clinical protocol for the determination of monocular alignment hyperacuity

Hyperacuity describes a variety of visual functions which are measured at thresholds smaller than expected given comparatively large receptor spacing and the subsequent predicted retinal image quality of the human eye. Monocular alignment hyperacuity is the ability to make very fine judgments of lateral or vertical displacement. There are numerous clinical uses for monocular alignment hyperacuity; however, there exists little procedural continuity among research in this area. This lack of continuity makes clinical adaptation and interpretation difficult. This project attempts to establish an efficient protocol for the measurement of monocular alignment hyperacuity in order to increase its clinical applicability and interpretability. Nineteen subjects each performed 300 trials at two testing distances using the method of subjective adjustment to alignment. The distribution of errors from alignment allow calculation of monocular alignment hyperacuity. Results indicate that a useful and consistent monocular alignment hyperacuity can be obtained in 250 trials on any cooperative subject or patient. Methods are suggested to decrease the number of trials necessary for clinical efficiency. Additionally, even though the angular subtense of the test stimuli were kept constant at one meter and six meters, the six meters testing distance yields lower thresholds (greater sensitivity) than that of the one meter distance, possibly due to increased peripheral cues to alignment

Solubility of precursors and carbonation of waterglass-free geopolymers

Geopolymers have the potential to function as an environmentally friendly substitute for ordinary Portland cement, with up to 80% less CO$_{2}$ emission during production. The effect is best utilized for geopolymers prepared with amorphous silica instead of waterglass (Na$_{2x}$Si$_{y}$O$_{2y+x}$) to adjust the Si:Al ratio. The reactivity of the precursors with the alkaline activator affects the final mineralogical properties of the binder. The purpose of the present study was to investigate the amount of different phases formed during geopolymerization and to understand the quantitative evolution of carbonation during geopolymer synthesis by determining the solubility of metakaolinite and amorphous SiO$_{2}$ in NaOH at various concentrations. The solubility was studied by ICP-OES measurements. X-ray diffraction was used for qualitative and quantitative phase analysis of the geopolymers. The solubility of the precursors increased with calcination temperature of metakaolinite, reaction time for amorphous SiO$_{2}$, and at higher NaOH concentrations. Partial dissolution resulted in free Na$^{+}$, which is a source for the formation of carbonates in the geopolymers. Thermonatrite occurred prior to trona formation in all samples

Geologische und STEEPLE-Aspekte zur überregionalen Verfügbarkeit von Rohstoffen zur Herstellung von Beton

Die weitere Zunahme der Weltbevölkerung und des Wohlstands wird bis zum Jahr 2060 zu einer Verdoppelung der Rohstoffexploration auf mindestens 86 Gt führen. Recycling allein wird den globalen Bedarf nicht decken können. Nutzungskonflikte können jedoch auch zukünftig verhindert werden, weil Baurohstoffe geologisch in ausreichender Menge verfügbar sind. Allerdings wird die Verfügbarkeit von qualitativ hochwertigem Kalkstein, Sand und Kies sowie Gips und Anhydrit für die Betonherstellung durch den anthropogenen Druck, die regionale Verteilung, politische, ökonomische, sozial-ethische, technologische, Umwelt und gesetzliche Aspekte begrenzt. Der Rückgang der Schwerindustrie und der Kohleverstromung in Deutschland führt zu geringeren verfügbaren Mengen an Hüttensand, Flugasche und REA-Gips. Deren Import, Substitution und neue Lagerstätten sind zur Deckung des Bedarfs der Bauindustrie notwendig. Der Anteil an R- (recycling) und M- (manufactured) Baustoffen kann erhöht werden, wenn Innovationen eine qualitativ hochwertige Sortierung gewährleisten. Der Megatrend Digitalisierung ermöglicht hierbei Effizienzsteigerungen in der Rohstoffgewinnung, der Bauindustrie, dem Recycling und an den Schnittstellen zu den Behörden. Die heimische Industrie kann bei geeigneten Randbedingungen auch mittelfristig den Rohstoffbedarf decken, globalem Protektionismus entgegenwirken und die Versorgungssicherheit gewährleisten. Eine attraktive und gesellschaftlich akzeptierte Rohstoffindustrie bündelt technisches Wissen und Innovation einer vertikalen Wertschöpfungskette bei Exploration, Produktion und Recycling. Langfristige Genehmigungsprozesse, unterschiedliche Nutzungsinteressen und die öffentliche Wahrnehmung erschweren die unternehmerische Tätigkeit. Auch eine Ausbildung im Bereich der Rohstoffexploration im Rohstoffland Deutschland wird weniger attraktiv. Damit gehen technisches Wissen und Innovationskraft sukzessive verloren

The Computational Complexity of Knot and Link Problems

We consider the problem of deciding whether a polygonal knot in 3-dimensional Euclidean space is unknotted, capable of being continuously deformed without self-intersection so that it lies in a plane. We show that this problem, {\sc unknotting problem} is in {\bf NP}. We also consider the problem, {\sc unknotting problem} of determining whether two or more such polygons can be split, or continuously deformed without self-intersection so that they occupy both sides of a plane without intersecting it. We show that it also is in NP. Finally, we show that the problem of determining the genus of a polygonal knot (a generalization of the problem of determining whether it is unknotted) is in {\bf PSPACE}. We also give exponential worst-case running time bounds for deterministic algorithms to solve each of these problems. These algorithms are based on the use of normal surfaces and decision procedures due to W. Haken, with recent extensions by W. Jaco and J. L. Tollefson.Comment: 32 pages, 1 figur

Loop operators and S-duality from curves on Riemann surfaces

We study Wilson-'t Hooft loop operators in a class of N=2 superconformal field theories recently introduced by Gaiotto. In the case that the gauge group is a product of SU(2) groups, we classify all possible loop operators in terms of their electric and magnetic charges subject to the Dirac quantization condition. We then show that this precisely matches Dehn's classification of homotopy classes of non-self-intersecting curves on an associated Riemann surface--the same surface which characterizes the gauge theory. Our analysis provides an explicit prediction for the action of S-duality on loop operators in these theories which we check against the known duality transformation in several examples.Comment: 41 page

Ionic and electronic properties of the topological insulator Bi2_2Te2_2Se investigated using β\beta-detected nuclear magnetic relaxation and resonance of 8^8Li

We report measurements on the high temperature ionic and low temperature electronic properties of the 3D topological insulator Bi$_2$Te$_2$Se using ion-implanted $^8$Li $\beta$-detected nuclear magnetic relaxation and resonance. With implantation energies in the range 5-28 keV, the probes penetrate beyond the expected range of the topological surface state, but are still within 250 nm of the surface. At temperatures above ~150 K, spin-lattice relaxation measurements reveal isolated $^8$Li$^{+}$ diffusion with an activation energy $E_{A} = 0.185(8)$ eV and attempt frequency $\tau_{0}^{-1} = 8(3) \times 10^{11}$ s$^{-1}$ for atomic site-to-site hopping. At lower temperature, we find a linear Korringa-like relaxation mechanism with a field dependent slope and intercept, which is accompanied by an anomalous field dependence to the resonance shift. We suggest that these may be related to a strong contribution from orbital currents or the magnetic freezeout of charge carriers in this heavily compensated semiconductor, but that conventional theories are unable to account for the extent of the field dependence. Conventional NMR of the stable host nuclei may help elucidate their origin.Comment: 17 pages, 12 figures, submitted to Phys. Rev.