18,529 research outputs found
Numerical solutions of several reflected shock-wave flow fields with nonequilibrium chemical reactions
The method of characteristics for a chemically reacting gas is used in the construction of the time-dependent, one-dimensional flow field resulting from the normal reflection of an incident shock wave at the end wall of a shock tube. Nonequilibrium chemical reactions are allowed behind both the incident and reflected shock waves. All the solutions are evaluated for oxygen, but the results are generally representative of any inviscid, nonconducting, and nonradiating diatomic gas. The solutions clearly show that: (1) both the incident- and reflected-shock chemical relaxation times are important in governing the time to attain steady state thermodynamic properties; and (2) adjacent to the end wall, an excess-entropy layer develops wherein the steady state values of all the thermodynamic variables except pressure differ significantly from their corresponding Rankine-Hugoniot equilibrium values
Evaluation of expected solar flare neutrino events in the IceCube observatory
Since the end of the eighties and in response to a reported increase in the
total neutrino flux in the Homestake experiment in coincidence with a solar
flare, solar neutrino detectors have searched for solar flare signals.
Neutrinos from the decay of mesons, which are themselves produced in collisions
of accelerated protons with the solar atmosphere, would provide a novel window
on the underlying physics of the acceleration process. For our studies we focus
on the IceCube Neutrino Observatory, a cubic kilometer neutrino detector
located at the geographical South Pole. Due to its Supernova data acquisition
system and its DeepCore component, dedicated to low energy neutrinos, IceCube
may be sensitive to solar flare neutrinos and thus permit either a measurement
of the signal or the establishment of more stringent upper limits on the solar
flare neutrino flux. We present an approach for a time profile analysis based
on a stacking method and an evaluation of a possible solar flare signal in
IceCube using the Geant4 toolkit.Comment: Paper submitted to the 34th International Cosmic Ray Conference, The
Hague 201
Kinetics of the reaction of nitric oxide with hydrogen
Mixtures of NO and H2 diluted in argon or krypton were heated by incident shock waves, and the infrared emission from the fundamental vibration-rotation band of NO at 5.3 microns was used to monitor the time-varying NO concentration. The reaction kinetics were studied in the temperature range 2400-4500 K using a shock-tube technique. The decomposition of nitric oxide behind the shock was found to be modeled well by a fifteen-reaction system. A principle result of the study was the determination of the rate constant for the reaction H + NO yields N + OH, which may be the rate-limiting step for NO removal in some combustion systems. Experimental values of k sub 1 were obtained for each test through comparisons of measured and numerically predicted NO profiles
Thermal integration of electrical power and life support systems for manned space stations
Thermal integration of life support and electrical power systems of six-man space station to obtain maximum utilization of waste energy from power generating syste
Feasibility study of a 110 watt per kilogram lightweight solar array system
An investigation of the feasibility of a solar array panel subsystem which will produce 10,000 watts of electrical output at 1 A.U. with an overall beginning-of-life power-to-weight ratio of at least 110 watt/kg is reported. A description of the current baseline configuration which meets these requirements is presented. A parametric analysis of the single boom, two blanket planar solar array system was performed to arrive at the optimum system aspect ratio. A novel concept for the stiffening of a lightweight solar array by canting the solar cell blankets at a small angle to take advantage of the inherent in-plane stiffness to increase the symmetric out-of-plane frequency is introduced along with a preliminary analysis of the stiffening effect. A comparison of welded and soldered solar cell interconnections leads to the conclusion that welding is required on this ultralightweight solar array. The use of a boron/aluminum composite material in a BI-STEM type deployable boom is investigated as a possible advancement in the state-of-the-art
Persistent Homology in Sparse Regression and its Application to Brain Morphometry
Sparse systems are usually parameterized by a tuning parameter that
determines the sparsity of the system. How to choose the right tuning parameter
is a fundamental and difficult problem in learning the sparse system. In this
paper, by treating the the tuning parameter as an additional dimension,
persistent homological structures over the parameter space is introduced and
explored. The structures are then further exploited in speeding up the
computation using the proposed soft-thresholding technique. The topological
structures are further used as multivariate features in the tensor-based
morphometry (TBM) in characterizing white matter alterations in children who
have experienced severe early life stress and maltreatment. These analyses
reveal that stress-exposed children exhibit more diffuse anatomical
organization across the whole white matter region.Comment: submitted to IEEE Transactions on Medical Imagin
Decomposition of NO studied by infrared emission and CO laser absorption
A diagnostic technique for monitoring the concentration of NO using absorption of CO laser radiation was developed and applied in a study of the decomposition kinetics of NO. Simultaneous measurements of infrared emission by NO at 5.3 microns were also made to validate the laser absorption technique. The data were obtained behind incident shocks in NO-N2O-Ar (or Kr) mixtures, with temperatures in the range 2400-4100 K. Rate constants for dominant reactions were inferred from comparisons with computer simulations of the reactive flow
Nation Dreaming: A Consideration of the American Dream in Poland, the U.S., and among Polish Americans
This paper examines the cooperation and influences between Poland and the U.S on their respective dreams, including the influence of the American Dream on Polish Americans and their potential distinctness from those who remain in Poland. Attitudes involving the American Dream that are examined include beliefs about freedom, liberty, democracy, getting ahead, status/mobility, and inequality. Although scholars have compared these belief systems across countries, there has been no distinct focus on Poland and the U.S., and those who immigrate between these countries. A conceptual framework that combines the American Dream, American exceptionalism, and beliefs about inequality guides the research. Data from the General Social Survey and the World Values Survey are used to answer the research questions. Findings show that Polish Americans agree with other Americans on a majority of items measuring elements of the American Dream. However, Americans and Poles have significantly different opinions on each of the American Dream items. Usually, (but not always) it is Americans who are more supportive of the American Dream. When considering the three groups, Polish Americans, Americans, and Poles, our conclusions suggest a trend where Polish Americans are a hybrid of other Americans and Poles when it comes to their views on the Dream. However, the differences often run in the direction that Polish Americans’ views are more like other Americans and distinct from Poles. Conclusions and implications are provided within the historical context of the long history of cooperation between the U.S. and Poland in fights for freedom and democracy
Spin filling of a quantum dot derived from excited-state spectroscopy
We study the spin filling of a semiconductor quantum dot using excited-state
spectroscopy in a strong magnetic field. The field is oriented in the plane of
the two-dimensional electron gas in which the dot is electrostatically defined.
By combining the observation of Zeeman splitting with our knowledge of the
absolute number of electrons, we are able to determine the ground state spin
configuration for one to five electrons occupying the dot. For four electrons,
we find a ground state spin configuration with total spin S=1, in agreement
with Hund's first rule. The electron g-factor is observed to be independent of
magnetic field and electron number.Comment: 11 pages, 7 figures, submitted to New Journal of Physics, focus issue
on Solid State Quantum Informatio
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