Study of advanced radial outflow turbine for solar steam Rankine engines

The performance characteristics of various steam Rankine engine configurations for solar electric power generation were investigated. A radial outflow steam turbine was investigated to determine: (1) a method for predicting performance from experimental data; (2) the flexibility of a single design with regard to power output and pressure ratio; and (3) the effect of varying the number of turbine stages. All turbine designs were restricted to be compatible with commercially available gearboxes and generators. A study of several operating methods and control schemes for the steam Rankine engine shows that from an efficiency and control simplicity standpoint, the best approach is to hold turbine inlet temperature constant, vary turbine inlet pressure to match load, and allow condenser temperature to float maintaining constant heat rejection load

Combined high vacuum/high frequency fatigue tester

Apparatus permits application of significantly greater number of cycles or equivalent number of cycles in shorter time than conventional fatigue test machines. Environment eliminates problems associated with high temperature oxidation and with sensitivity of refractory alloy behavior to atmospheric contamination

Conditioning of pulses from aerosol-particle detectors

Pulse-conditioner translates pulses generated by aerosol-particle detectors to a form acceptable by commercially available pulse height analyzers designed for nuclear-energy spectroscopy

Automated weighing by sequential inference in dynamic environments

We demonstrate sequential mass inference of a suspended bag of milk powder from simulated measurements of the vertical force component at the pivot while the bag is being filled. We compare the predictions of various sequential inference methods both with and without a physics model to capture the system dynamics. We find that non-augmented and augmented-state unscented Kalman filters (UKFs) in conjunction with a physics model of a pendulum of varying mass and length provide rapid and accurate predictions of the milk powder mass as a function of time. The UKFs outperform the other method tested - a particle filter. Moreover, inference methods which incorporate a physics model outperform equivalent algorithms which do not.Comment: 5 pages, 7 figures. Copyright IEEE (2015

Luminosities and mass-loss rates of Local Group AGB stars and Red Supergiants

We aim to investigate mass loss and luminosity in a large sample of evolved stars in several Local Group galaxies with a variety of metalliticies and star-formation histories: the Small and Large Magellanic Cloud, and the Fornax, Carina, and Sculptor dwarf spheroidal galaxies. Dust radiative transfer models are presented for 225 carbon stars and 171 oxygen-rich evolved stars for which spectra from the Infrared Spectrograph on Spitzer are available. The spectra are complemented with available optical and infrared photometry to construct spectral energy distributions. A minimization procedure was used to determine luminosity and mass-loss rate (MLR). Pulsation periods were derived for a large fraction of the sample based on a re-analysis of existing data. New deep K-band photometry from the VMC survey and multi-epoch data from IRAC and AllWISE/NEOWISE have allowed us to derive pulsation periods longer than 1000 days for some of the most heavily obscured and reddened objects. We derive (dust) MLRs and luminosities for the entire sample. The estimated MLRs can differ significantly from estimates for the same objects in the literature due to differences in adopted optical constants (up to factors of several) and details in the radiative transfer modelling. Updated parameters for the super-AGB candidate MSX SMC 055 (IRAS 00483-7347) are presented. Its current mass is estimated to be 8.5 +- 1.6 \msol, suggesting an initial mass well above 8~\msol. Using synthetic photometry, we present and discuss colour-colour and colour-magnitude diagrams which can be expected from the James Webb Space Telescope.Comment: A&A accepted. The full version (100 pages, 12 MB) with complete tables and all figures of the appendices is available at http://homepage.oma.be/marting/articlesgroen.htm

Electronic Hong-Ou-Mandel interferometry in two-dimensional topological insulators

The edge states of a two-dimensional topological insulator are characterized by their helicity, a very remarkable property which is related to the time-reversal symmetry and the topology of the underlying system. We theoretically investigate a Hong-Ou-Mandel like setup as a tool to probe it. Collisions of two electrons with the same spin show a Pauli dip, analogous to the one obtained in the integer quantum Hall case. Moreover, the collisions between electrons of opposite spin also lead to a dip, known as $\mathbb{Z}_{2}$ dip, which is a direct consequence of the constraints imposed by time-reversal symmetry. In contrast to the integer quantum Hall case, the visibility of these dips is reduced by the presence of the additional edge channels, and crucially depends on the properties of the quantum point contact. As a unique feature of this system, we show the possibility of three-electron interference, which leads to a total suppression of the noise independently of the point contact configuration. This is assured by the peculiar interplay between Fermi statistics and topology. This work intends to extend the domain of applicability of electron quantum optics.Comment: 12 pages, 7 figure

On the Disalignment of Interstellar Grains

Several mechanisms have been proposed to explain the alignment of grains with the interstellar magnetic field, including paramagnetic dissipation, radiative torques, and supersonic gas-grain streaming. These must compete with disaligning processes, including randomly directed torques arising from collisions with gas atoms. I describe a novel disalignment mechanism for grains that have a time-varying electric dipole moment and that drift across the magnetic field. Depending on the drift speed, this mechanism may yield a much shorter disalignment timescale than that associated with random gas atom impacts. For suprathermally rotating grains, the new disaligning process may be more potent for carbonaceous dust than for silicate dust. This could result in efficient alignment for silicate grains but poor alignment for carbonaceous grains.Comment: 19 pages, 3 figures, submitted to Ap

Numerical residual perturbation solution applied to an earth satellite including luni-solar effects

Mathematical model and computer program for numerical solution of earth orbit differential equations of motio

Experimental constraints on the polarizabilities of the 6s^2 1S0 and 6s6p 3P0 states of Yb

We utilize accurate experimental data available in the literature to yield bounds on the polarizabilities of the ground and first excited states of atomic Yb. For the 6s^2 1S0 ground state, we find the polarizability alpha to be constrained to 134.4<alpha<144.2 in atomic units, while for the 6s6p 3P0 excited state we find 280.1<alpha<289.9. The uncertainty in each of these values is 1.0. These constraints provide a valuable check for ab initio and semi-empirical methods used to compute polarizabilities and other related properties in Yb.Comment: 7 pages, 1 figur