Abundances in Damped Ly-alpha Galaxies

Damped Ly_alpha galaxies provide a sample of young galaxies where chemical abundances can be derived throughout the whole universe with an accuracy comparable to that for the local universe. Despite a large spread in redshift, HI column density and metallicity, DLA galaxies show a remarkable uniformity in the elemental ratios rather suggestive of similar chemical evolution if not of an unique population. These galaxies are characterized by a moderate, if any, enhancement of alpha-elements over Fe-peak elemental abundance with [S/Zn] about 0 and [O/Zn] about 0.2, rather similarly to the dwarfs galaxies in the Local Group. Nitrogen shows a peculiar behaviour with a bimodal distribution and possibly two plateaux. In particular, the plateau at low N abundances ([N/H] < -3), is not observed in other atrophysical sites and might be evidence for primary N production by massive stars.Comment: To appear in the Proceedings of the ESO/Arcetri Workshop on "Chemical Abundances and Mixing in Stars in the Milky Way and its Satellites", eds., L. Pasquini and S. Randich (Springer-Verlag Series, "ESO Astrophysics Symposia"

Solar Power Satellite antenna phase control system hardware simulation, phase 4: Volume 1: Executive summary

The phase control system is described. Potential sources of phase error are identified and the performance leading to selection of the allowable phase error for each source is summarized. The pilot transmitter, the effects of ionospheric, the master slave returnable timing system (MSRTS), the SPS receiver, and the high power amplifier for dc to microwave conversion are considered separately. Design parameters of the pilot transmitter and spacetenna transponder are presented

SPS pilot signal design and power transponder analysis, volume 2, phase 3

The problem of pilot signal parameter optimization and the related problem of power transponder performance analysis for the Solar Power Satellite reference phase control system are addressed. Signal and interference models were established to enable specifications of the front end filters including both the notch filter and the antenna frequency response. A simulation program package was developed to be included in SOLARSIM to perform tradeoffs of system parameters based on minimizing the phase error for the pilot phase extraction. An analytical model that characterizes the overall power transponder operation was developed. From this model, the effects of different phase noise disturbance sources that contribute to phase variations at the output of the power transponders were studied and quantified. Results indicate that it is feasible to hold the antenna array phase error to less than one degree per power module for the type of disturbances modeled

Solar Power Satellite antenna phase control system hardware simulation, phase 4. Volume 2: Analytical simulation of SPS system performance

The pilot signal parameter optimization and power transponder analyses are presented. The SPS antenna phase control system is modeled and the hardware simulation study described. Ionospheric and system phase error effects and the effects of high power amplifier phase and amplitude jitters are considered. Parameter optimization of the spread spectrum receiver, consisting of the carrier tracking loop and the code tracking loop, is described

SPS phase control system performance via analytical simulation

A solar power satellite transmission system which incorporates automatic beam forming, steering, and phase control is discussed. The phase control concept centers around the notation of an active retrodirective phased array as a means of pointing the beam to the appropriate spot on Earth. The transmitting antenna (spacetenna) directs the high power beam so that it focuses on the ground-based receiving antenna (rectenna). A combination of analysis and computerized simulation was conducted to determine the far field performance of the reference distribution system, and the beam forming and microwave power generating systems

Autonomous Integrated Receive System (AIRS) requirements definition. Volume 2: Design and development

Functional requirements and specifications are defined for an autonomous integrated receive system (AIRS) to be used as an improvement in the current tracking and data relay satellite system (TDRSS), and as a receiving system in the future tracking and data acquisition system (TDAS). The AIRS provides improved acquisition, tracking, bit error rate (BER), RFI mitigation techniques, and data operations performance compared to the current TDRSS ground segment receive system. A computer model of the AIRS is used to provide simulation results predicting the performance of AIRS. Cost and technology assessments are included

Optimization Of Process Parameters On Tensile Shear Load Of Friction Stir Spot Welded Aluminum Alloy (Aa5052-h112)

Optimization of the process was still the issue in manufacturing. Investigation on the process parameters that effects to the property of welded structure were necessary. In this study, the AA5052-H32 sheets of 2 mm thick were welded using friction stir spot welding (FSSW) and tested via tensile shear load test to investigate the influence of spindle speed, tool depth, and dwell time to the tensile shear load of the joints. The result shows that in every set of parameter combination, exhibit interesting influence to the tensile shear load. The effect of spindle speed of 1000 rpm shown the good property in average 18.33 KN especially at tool depth of 3.5 mm. Furthermore, the effect of tool depth brought significant effect to the tensile shear load especially at 3.5 mm for each set of spindle speed and dwell time. The set of dwell time to parameter combination had no significant effect to the tensile shear load. The good tensile shear load could be achieved in the range of 17.7-19.3 KN at 3.5 mm of plunge depth and 1000 rpm of spindle speed, where the best one was 19.3 KN at 7s of dwell time

Orthonormal Polynomials on the Unit Circle and Spatially Discrete Painlev\'e II Equation

We consider the polynomials $\phi_n(z)= \kappa_n (z^n+ b_{n-1} z^{n-1}+ >...)$ orthonormal with respect to the weight $\exp(\sqrt{\lambda} (z+ 1/z)) dz/2 \pi i z$ on the unit circle in the complex plane. The leading coefficient $\kappa_n$ is found to satisfy a difference-differential (spatially discrete) equation which is further proved to approach a third order differential equation by double scaling. The third order differential equation is equivalent to the Painlev\'e II equation. The leading coefficient and second leading coefficient of $\phi_n(z)$ can be expressed asymptotically in terms of the Painlev\'e II function.Comment: 16 page

Mien-Chie Hung, PhD, Oral History Interview, February 20, 2014

Major Topics Covered: Personal and educational background; witty and humorous personal stories Experiences of a Chinese immigrant and foreign graduate student The working strategies, inspirations, and commitment of a basic/translational scientist Research: signaling pathways and genes, Department of Molecular and Cellular Oncology: history, evolution, personal vision for Research culture at MD Anderson Vice President of Basic Research The Institute for Basic Science Effective leadership and mentoring Training young scientistshttps://openworks.mdanderson.org/mchv_interviewsessions/1151/thumbnail.jp