Bench-Scale Study of Sulfur and Nitrogen Oxides Absoption by Nahcolite and Trona

The extent and rates of sulfur and nitrogen oxides \u27dry\u27 adsorption by nahcolite and trona were measured. Experiments were conducted by passing simulated flue gas through a fixed bed of test material. Variables considered in the study were particle size, reaction temperature, concentration of sulfur dioxide, and concentration of water vapor in the flue gas. High reaction rates were noted for the adsorption of sulfur dioxide by nahcolite at reaction temperatures of 400-650° F and for particle diameters of 0.19 mm or less. Based on the adsorption of sulfur dioxide, certain tests resulted in nahcolite utilizations of over 95 pet. Trona also proved to be capable of adsorbing sulfur dioxide. However, reaction rates and utilizations were considerably lower. Neither nahcolite or trona proved to be an effective adsorbent of nitrogen oxide. Water vapor concentrations of 5 to 15 volume percent had no significant effect on reaction rates or utilizations. For the nahcolite-sulfur dioxide reaction both chemical reaction and gas diffusion through the ash layer mechanisms contributed major resistances in controlling the overall reaction rate. The high reaction rates and utilizations determined for the nahcolitesulfur dioxide reaction indicate that nahcolite has great potential as a sorbent for \u27dry\u27 flue gas desulfurization

Towards the high-fidelity multidisciplinary design optimization of a 3d composite material hydrofoil

The development of a multidisciplinary design optimization (MDO) architecture for high-fidelity fluid-structure interaction (FSI) problems is presented with preliminary application to a NACA 0009 3D hydrofoil in metal and carbon-fiber reinforced plastic materials. The MDO methodology and FSI benchmark solution are presented and discussed. The computational cost of the MDO is reduced by performing a design space dimensionality reduction beforehand and integrating into the architecture a variable level of coupling between disciplines, a surrogate model, and an adaptive sampling technique. The optimization is performed using a heuristic global derivative-free algorithm. The MDO method is demonstrated by application to an analytical test problem. Current stage of research includes preliminary test problem optimization, validation of the hydrofoil FSI against experimental data, and design space assessment and dimensionality reduction for the hydrofoil model

The Lengths of Psychiatric Hospital Stays and Community Stays

We use advanced survival analysis methods to estimate the parameters affecting the joint distribution of exit dates from psychiatric hospitals and return dates to those hospitals. Data comes from Virginia state psychiatric hospital administrative records. We find that sex, marital status, employment status, diagnosis, and age help explain durations. We also find that there is significant duration dependence and unobserved heterogeneity which suggest that earlier analyses in this field that used simpler estimation methods were flawed.

Small-scale Intensity Mapping: Extended Halos as a Probe of the Ionizing Escape Fraction and Faint Galaxy Populations during Reionization

We present a new method to quantify the value of the escape fraction of ionizing photons, and the existence of ultra-faint galaxies clustered around brighter objects during the epoch of cosmic reionization, using the diffuse Ly$\alpha$, continuum and H$\alpha$ emission observed around galaxies at $z\sim6$. We model the surface brightness profiles of the diffuse halos considering the fluorescent emission powered by ionizing photons escaping from the central galaxies, and the nebular emission from satellite star-forming sources, by extending the formalisms developed in Mas-Ribas & Dijkstra (2016) and Mas-Ribas et al. (2017). The comparison between our predicted profiles and Ly$\alpha$ observations at $z=5.7$ and $z=6.6$ favors a low ionizing escape fraction, $f_{\rm esc}^{\rm ion}\sim5\%$, for galaxies in the range $-19\gtrsim M_{\rm UV} \gtrsim -21.5$. However, uncertainties and possible systematics in the observations do not allow for firm conclusions. We predict H$\alpha$ and rest-frame visible continuum observations with JWST, and show that JWST will be able to detect extended (a few tens of kpc) fluorescent H$\alpha$ emission powered by ionizing photons escaping from a bright, $L\gtrsim 5L^*$, galaxy. Such observations can differentiate fluorescent emission from nebular emission by satellite sources. We discuss how observations and stacking of several objects may provide unique constraints on the escape fraction for faint galaxies and/or the abundance of ultra-faint radiation sources.Comment: 9 pages, 4 figures, re-submitted after referee report to Ap

Calm Water and Seakeeping Investigation for a Fast Catamaran

In this paper calm water and in wave research activities on a high-speed displacement catamaran performed at CNRINSEAN in collaboration with the IIHR are presented. The selected geometry is the DELFT-372 catamaran, for which a large database is in construction through a series of NICOP projects. Calm water activity was carried out for the analysis of the interference phenomena; resistance, trim and sinkage tests have been performed for both the monohull and the catamaran with several separation lengths and for a wide range of Froude numbers (Fr=0.1?0.8). Experimental (inner and outer) wave cuts have been also acquired for selected separation lengths and Froude numbers. Seakeeping tests with transient, regular and irregular waves are performed. Preliminarily, comparison with the experimental results in regular wave carried out at DELFT have been done. Seakeeping transient tests allowed the identification of the Froude number of maximum response; once it has been determined, regular wave experiments were used to assess the role of the nonlinearities on the hull motions at that Fr: several steepness and wavelengths of the incident wave system were considered. The measurements collected are a valuable data base for both hydrodynamic studies of high speed catamaran and CFD validation

Validation of high fidelity CFD/FE FSI for full-scale high-speed planing hull with composite bottom panels slamming

High fidelity CFD/FE FSI (Computational Fluid Dynamics/Finite Element FluidStructure Interaction) code development and validation by full-scale experiments is presented, for the analysis of hydrodynamic and structural slamming responses. A fully instrumented 9 meter high speed-planing hull with sterndrive is used. Starboard and port bottom panels are constructed with different composite materials and fiber orientations, allowing for study of the relation between structural properties and slamming. The code CFDShip-Iowa is employed for CFD simulations and the commercial FE code ANSYS is used as structural solver. The hydrodynamic simulations include captive (2DOF without sterndrive) and 6DOF free running conditions for various Froude numbers in calm water and regular waves. Calm water simulations compares well with the experimental data and 1D empirical data provided by the sterndrive manufacturer for resistance, heave, pitch and roll motions. Numerical one-way coupling FSI is performed in head and following regular waves representative of sea-trial conditions, using FE models for two bottom panels. The resulting strains are compared with experimental data showing a good qualitative and quantitative agreement

CFD, potential flow and system-based simulations of fully appended free running 5415m in calm water and waves

5415M, course-keeping, waves, CFD, validation, NATO AVT-161 Abstract. The seakeeping ability of ships is one of the aspects that needs to be assessed during the design phase of ships. Traditionally, potential flow calculations and model tests are employed to investigate whether the ship performs according to specified criteria. With the increase of computational power nowadays, advanced computational tools such as Computational Fluid Dynamics (CFD) become within reach of application during the assessment of ship designs. In the present paper, a detailed validation study of several computational methods for ship dynamics is presented. These methods range from low-fidelity system-based methods, to potential flow methods, to high-fidelity CFD tools. The ability of the methods to predict motions in calm water as well as in waves is investigated. In calm water, the roll decay behavior of a fully appended self-propelled free running 5415M model is investigated first. Subsequently, forced roll motions simulated by oscillating the rudders or stabilizer fins are studied. Lastly, the paper discusses comparisons between experiments and simulations in waves with varying levels of complexity, i.e. regular head waves, regular beam waves and bi-chromatic waves. The predictions for all methods are validated with an extensive experimental data set for ship motions and loads on appendages such as rudders, fins and bilge keels. Comparisons between the different methods and with the experiments are made for the relevant motions and the high fidelity CFD results are used to explain some of the complex physics. The course keeping and seakeeping of the model, the reduction rate of the roll motion, the effectiveness of the fin stabilizers as roll reduction device and the interaction of the roll motion with other motions are investigated as well. The paper shows that only high-fidelity CFD is able to accurately predict all the relevant physics during roll decay, forced oscillation and sailing in waves

NuSTAR study of Hard X-Ray Morphology and Spectroscopy of PWN G21.5-0.9

We present NuSTAR high energy X-ray observations of the pulsar wind nebula (PWN)/supernova remnant G21.5-0.9. We detect integrated emission from the nebula up to ~40 keV, and resolve individual spatial features over a broad X-ray band for the first time. The morphology seen by NuSTAR agrees well with that seen by XMM-Newton and Chandra below 10 keV. At high energies NuSTAR clearly detects non-thermal emission up to ~20 keV that extends along the eastern and northern rim of the supernova shell. The broadband images clearly demonstrate that X-ray emission from the North Spur and Eastern Limb results predominantly from non-thermal processes. We detect a break in the spatially integrated X-ray spectrum at ~9 keV that cannot be reproduced by current SED models, implying either a more complex electron injection spectrum or an additional process such as diffusion compared to what has been considered in previous work. We use spatially resolved maps to derive an energy-dependent cooling length scale, $L(E) \propto E^{m}$ with $m = -0.21 \pm 0.01$. We find this to be inconsistent with the model for the morphological evolution with energy described by Kennel & Coroniti (1984). This value, along with the observed steepening in power-law index between radio and X-ray, can be quantitatively explained as an energy-loss spectral break in the simple scaling model of Reynolds (2009), assuming particle advection dominates over diffusion. This interpretation requires a substantial departure from spherical magnetohydrodynamic (MHD), magnetic-flux-conserving outflow, most plausibly in the form of turbulent magnetic-field amplification.Comment: 13 pages, 8 figures, 1 table, Accepted for publication in the Astrophysical Journa